diff --git a/.changeset/silver-boxes-flash.md b/.changeset/silver-boxes-flash.md
new file mode 100644
index 0000000000..9f30c1a34b
--- /dev/null
+++ b/.changeset/silver-boxes-flash.md
@@ -0,0 +1,9 @@
+---
+'@backstage/plugin-catalog-react': patch
+---
+
+**BREAKING**: Moved **DefaultStarredEntitiesApi** to `@backstage/plugin-catalog`. If you were using this in tests, you can use the new `MockStarredEntitiesApi` from `@backstage/plugin-catalog-react` instead.
+
+Fixed a risky behavior where `DefaultStarredEntitiesApi` forwarded values to observers that were later mutated.
+
+Removed the `isStarred` method from `DefaultStarredEntitiesApi`, as it is not part of the `StarredEntitiesApi`.
diff --git a/packages/app/src/components/catalog/EntityPage.test.tsx b/packages/app/src/components/catalog/EntityPage.test.tsx
index b68b9e9895..68ce5fb497 100644
--- a/packages/app/src/components/catalog/EntityPage.test.tsx
+++ b/packages/app/src/components/catalog/EntityPage.test.tsx
@@ -16,15 +16,14 @@
 
 import { EntityLayout } from '@backstage/plugin-catalog';
 import {
-  DefaultStarredEntitiesApi,
   EntityProvider,
   starredEntitiesApiRef,
+  MockStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
 import { githubActionsApiRef } from '@backstage/plugin-github-actions';
 import { permissionApiRef } from '@backstage/plugin-permission-react';
 import {
   MockPermissionApi,
-  MockStorageApi,
   renderInTestApp,
   TestApiProvider,
 } from '@backstage/test-utils';
@@ -59,12 +58,7 @@ describe('EntityPage Test', () => {
         <TestApiProvider
           apis={[
             [githubActionsApiRef, mockedApi],
-            [
-              starredEntitiesApiRef,
-              new DefaultStarredEntitiesApi({
-                storageApi: MockStorageApi.create(),
-              }),
-            ],
+            [starredEntitiesApiRef, new MockStarredEntitiesApi()],
             [permissionApiRef, mockPermissionApi],
           ]}
         >
diff --git a/plugins/api-docs/src/components/ApiExplorerPage/DefaultApiExplorerPage.test.tsx b/plugins/api-docs/src/components/ApiExplorerPage/DefaultApiExplorerPage.test.tsx
index 16b335b0a7..5924af3ef3 100644
--- a/plugins/api-docs/src/components/ApiExplorerPage/DefaultApiExplorerPage.test.tsx
+++ b/plugins/api-docs/src/components/ApiExplorerPage/DefaultApiExplorerPage.test.tsx
@@ -22,11 +22,13 @@ import {
   configApiRef,
   storageApiRef,
 } from '@backstage/core-plugin-api';
-import { CatalogTableRow } from '@backstage/plugin-catalog';
+import {
+  CatalogTableRow,
+  DefaultStarredEntitiesApi,
+} from '@backstage/plugin-catalog';
 import {
   CatalogApi,
   catalogApiRef,
-  DefaultStarredEntitiesApi,
   entityRouteRef,
   starredEntitiesApiRef,
 } from '@backstage/plugin-catalog-react';
diff --git a/plugins/catalog-react/api-report.md b/plugins/catalog-react/api-report.md
index e78ec75daa..3e1136313f 100644
--- a/plugins/catalog-react/api-report.md
+++ b/plugins/catalog-react/api-report.md
@@ -24,7 +24,6 @@ import { default as React_2 } from 'react';
 import { ReactNode } from 'react';
 import { RouteRef } from '@backstage/core-plugin-api';
 import { ScmIntegrationRegistry } from '@backstage/integration';
-import { StorageApi } from '@backstage/core-plugin-api';
 import { StyleRules } from '@material-ui/core/styles/withStyles';
 import { SystemEntity } from '@backstage/catalog-model';
 import { TableColumn } from '@backstage/core-components';
@@ -138,17 +137,6 @@ export type DefaultEntityFilters = {
   text?: EntityTextFilter;
 };
 
-// @public
-export class DefaultStarredEntitiesApi implements StarredEntitiesApi {
-  constructor(opts: { storageApi: StorageApi });
-  // (undocumented)
-  isStarred(entityRef: string): boolean;
-  // (undocumented)
-  starredEntitie$(): Observable<Set<string>>;
-  // (undocumented)
-  toggleStarred(entityRef: string): Promise<void>;
-}
-
 // @public (undocumented)
 export type EntityFilter = {
   getCatalogFilters?: () => Record<
@@ -488,6 +476,14 @@ export const MockEntityListContextProvider: ({
   value?: Partial<EntityListContextProps<DefaultEntityFilters>> | undefined;
 }>) => JSX.Element;
 
+// @public
+export class MockStarredEntitiesApi implements StarredEntitiesApi {
+  // (undocumented)
+  starredEntitie$(): Observable<Set<string>>;
+  // (undocumented)
+  toggleStarred(entityRef: string): Promise<void>;
+}
+
 // @public @deprecated (undocumented)
 export function reduceCatalogFilters(
   filters: EntityFilter[],
diff --git a/plugins/catalog-react/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.test.ts b/plugins/catalog-react/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.test.ts
deleted file mode 100644
index 55b992fadf..0000000000
--- a/plugins/catalog-react/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.test.ts
+++ /dev/null
@@ -1,103 +0,0 @@
-/*
- * Copyright 2021 The Backstage Authors
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-import { stringifyEntityRef } from '@backstage/catalog-model';
-import { StorageApi } from '@backstage/core-plugin-api';
-import { MockStorageApi } from '@backstage/test-utils';
-import { DefaultStarredEntitiesApi } from './DefaultStarredEntitiesApi';
-import { performMigrationToTheNewBucket } from './migration';
-
-jest.mock('./migration');
-
-describe('DefaultStarredEntitiesApi', () => {
-  let mockStorage: StorageApi;
-  let starredEntitiesApi: DefaultStarredEntitiesApi;
-
-  const mockEntityRef = stringifyEntityRef({
-    apiVersion: '1',
-    kind: 'Component',
-    metadata: {
-      name: 'mock',
-    },
-  });
-
-  beforeEach(() => {
-    (performMigrationToTheNewBucket as jest.Mock).mockResolvedValue(undefined);
-
-    mockStorage = MockStorageApi.create();
-    starredEntitiesApi = new DefaultStarredEntitiesApi({
-      storageApi: mockStorage,
-    });
-  });
-
-  afterEach(() => {
-    jest.resetAllMocks();
-  });
-
-  describe('constructor', () => {
-    it('should call migration', () => {
-      expect(performMigrationToTheNewBucket).toBeCalledTimes(1);
-    });
-  });
-
-  describe('toggleStarred', () => {
-    it('should star unstarred entity', async () => {
-      expect(starredEntitiesApi.isStarred(mockEntityRef)).toBe(false);
-
-      await starredEntitiesApi.toggleStarred(mockEntityRef);
-
-      expect(starredEntitiesApi.isStarred(mockEntityRef)).toBe(true);
-    });
-
-    it('should unstar starred entity', async () => {
-      const bucket = mockStorage.forBucket('starredEntities');
-      await bucket.set('entityRefs', ['component:default/mock']);
-
-      expect(starredEntitiesApi.isStarred(mockEntityRef)).toBe(true);
-
-      await starredEntitiesApi.toggleStarred(mockEntityRef);
-
-      expect(starredEntitiesApi.isStarred(mockEntityRef)).toBe(false);
-    });
-  });
-
-  describe('starredEntities$', () => {
-    const handler = jest.fn();
-
-    beforeEach(async () => {
-      await new Promise<void>(resolve => {
-        starredEntitiesApi.starredEntitie$().subscribe({
-          next: (...args) => {
-            handler(...args);
-
-            if (handler.mock.calls.length >= 2) {
-              resolve();
-            }
-          },
-        });
-
-        const bucket = mockStorage.forBucket('starredEntities');
-        bucket.set('entityRefs', ['component:default/mock']).then();
-      });
-    });
-
-    it('should receive updates', async () => {
-      expect(handler).toBeCalledTimes(2);
-      expect(handler).toBeCalledWith(new Set());
-      expect(handler).toBeCalledWith(new Set(['component:default/mock']));
-    });
-  });
-});
diff --git a/plugins/catalog-react/src/apis/StarredEntitiesApi/MockStarredEntitiesApi.test.ts b/plugins/catalog-react/src/apis/StarredEntitiesApi/MockStarredEntitiesApi.test.ts
new file mode 100644
index 0000000000..aadecefe98
--- /dev/null
+++ b/plugins/catalog-react/src/apis/StarredEntitiesApi/MockStarredEntitiesApi.test.ts
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { MockStarredEntitiesApi } from './MockStarredEntitiesApi';
+
+describe('MockStarredEntitiesApi', () => {
+  it('should toggle starred entities', async () => {
+    const api = new MockStarredEntitiesApi();
+
+    const updates1 = new Array<Set<string>>();
+    const sub1 = api
+      .starredEntitie$()
+      .subscribe(entities => updates1.push(entities));
+
+    api.toggleStarred('k:ns/e1');
+    api.toggleStarred('k:ns/e2');
+
+    await Promise.resolve();
+    expect(updates1).toEqual([
+      new Set(),
+      new Set(['k:ns/e1']),
+      new Set(['k:ns/e1', 'k:ns/e2']),
+    ]);
+
+    const updates2 = new Array<Set<string>>();
+    const sub2 = api
+      .starredEntitie$()
+      .subscribe(entities => updates2.push(entities));
+
+    api.toggleStarred('k:ns/e2');
+    sub1.unsubscribe();
+    api.toggleStarred('k:ns/e2');
+
+    await Promise.resolve();
+    expect(updates1).toEqual([
+      new Set(),
+      new Set(['k:ns/e1']),
+      new Set(['k:ns/e1', 'k:ns/e2']),
+      new Set(['k:ns/e1']),
+    ]);
+    expect(updates2).toEqual([
+      new Set(['k:ns/e1', 'k:ns/e2']),
+      new Set(['k:ns/e1']),
+      new Set(['k:ns/e1', 'k:ns/e2']),
+    ]);
+    sub2.unsubscribe();
+  });
+});
diff --git a/plugins/catalog-react/src/apis/StarredEntitiesApi/MockStarredEntitiesApi.ts b/plugins/catalog-react/src/apis/StarredEntitiesApi/MockStarredEntitiesApi.ts
new file mode 100644
index 0000000000..9467153dd9
--- /dev/null
+++ b/plugins/catalog-react/src/apis/StarredEntitiesApi/MockStarredEntitiesApi.ts
@@ -0,0 +1,54 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Observable } from '@backstage/types';
+import ObservableImpl from 'zen-observable';
+import { StarredEntitiesApi } from './StarredEntitiesApi';
+
+/**
+ * An in-memory mock implementation of the StarredEntitiesApi.
+ *
+ * @public
+ */
+export class MockStarredEntitiesApi implements StarredEntitiesApi {
+  private readonly starredEntities = new Set<string>();
+  private readonly subscribers = new Set<
+    ZenObservable.SubscriptionObserver<Set<string>>
+  >();
+
+  private readonly observable = new ObservableImpl<Set<string>>(subscriber => {
+    subscriber.next(new Set(this.starredEntities));
+
+    this.subscribers.add(subscriber);
+    return () => {
+      this.subscribers.delete(subscriber);
+    };
+  });
+
+  async toggleStarred(entityRef: string): Promise<void> {
+    if (!this.starredEntities.delete(entityRef)) {
+      this.starredEntities.add(entityRef);
+    }
+
+    for (const subscription of this.subscribers) {
+      subscription.next(new Set(this.starredEntities));
+    }
+  }
+
+  starredEntitie$(): Observable<Set<string>> {
+    return this.observable;
+  }
+}
diff --git a/plugins/catalog-react/src/apis/StarredEntitiesApi/index.ts b/plugins/catalog-react/src/apis/StarredEntitiesApi/index.ts
index e9f9c8923a..ba44c38e1d 100644
--- a/plugins/catalog-react/src/apis/StarredEntitiesApi/index.ts
+++ b/plugins/catalog-react/src/apis/StarredEntitiesApi/index.ts
@@ -14,6 +14,6 @@
  * limitations under the License.
  */
 
-export { DefaultStarredEntitiesApi } from './DefaultStarredEntitiesApi';
 export { starredEntitiesApiRef } from './StarredEntitiesApi';
 export type { StarredEntitiesApi } from './StarredEntitiesApi';
+export { MockStarredEntitiesApi } from './MockStarredEntitiesApi';
diff --git a/plugins/catalog-react/src/hooks/useEntityListProvider.test.tsx b/plugins/catalog-react/src/hooks/useEntityListProvider.test.tsx
index c8ca29b07f..27fde81cc7 100644
--- a/plugins/catalog-react/src/hooks/useEntityListProvider.test.tsx
+++ b/plugins/catalog-react/src/hooks/useEntityListProvider.test.tsx
@@ -29,7 +29,7 @@ import qs from 'qs';
 import React, { PropsWithChildren } from 'react';
 import { MemoryRouter } from 'react-router';
 import { catalogApiRef } from '../api';
-import { DefaultStarredEntitiesApi, starredEntitiesApiRef } from '../apis';
+import { starredEntitiesApiRef, MockStarredEntitiesApi } from '../apis';
 import { EntityKindPicker, UserListPicker } from '../components';
 import { EntityKindFilter, EntityTypeFilter, UserListFilter } from '../filters';
 import { UserListFilterKind } from '../types';
@@ -95,12 +95,7 @@ const wrapper = ({
           [catalogApiRef, mockCatalogApi],
           [identityApiRef, mockIdentityApi],
           [storageApiRef, MockStorageApi.create()],
-          [
-            starredEntitiesApiRef,
-            new DefaultStarredEntitiesApi({
-              storageApi: MockStorageApi.create(),
-            }),
-          ],
+          [starredEntitiesApiRef, new MockStarredEntitiesApi()],
         ]}
       >
         <EntityListProvider>
diff --git a/plugins/catalog-react/src/hooks/useStarredEntities.test.tsx b/plugins/catalog-react/src/hooks/useStarredEntities.test.tsx
index aef876a1b2..16fa19a1cd 100644
--- a/plugins/catalog-react/src/hooks/useStarredEntities.test.tsx
+++ b/plugins/catalog-react/src/hooks/useStarredEntities.test.tsx
@@ -15,15 +15,18 @@
  */
 
 import { Entity } from '@backstage/catalog-model';
-import { StorageApi } from '@backstage/core-plugin-api';
-import { MockStorageApi, TestApiProvider } from '@backstage/test-utils';
+import { TestApiProvider } from '@backstage/test-utils';
 import { act, renderHook } from '@testing-library/react-hooks';
 import React, { PropsWithChildren } from 'react';
-import { DefaultStarredEntitiesApi, starredEntitiesApiRef } from '../apis';
+import {
+  starredEntitiesApiRef,
+  StarredEntitiesApi,
+  MockStarredEntitiesApi,
+} from '../apis';
 import { useStarredEntities } from './useStarredEntities';
 
 describe('useStarredEntities', () => {
-  let mockStorage: StorageApi;
+  let mockApi: StarredEntitiesApi;
   let wrapper: React.ComponentType;
 
   const mockEntity: Entity = {
@@ -44,22 +47,15 @@ describe('useStarredEntities', () => {
   };
 
   beforeEach(() => {
-    mockStorage = MockStorageApi.create();
+    mockApi = new MockStarredEntitiesApi();
     wrapper = ({ children }: PropsWithChildren<{}>) => (
-      <TestApiProvider
-        apis={[
-          [
-            starredEntitiesApiRef,
-            new DefaultStarredEntitiesApi({ storageApi: mockStorage }),
-          ],
-        ]}
-      >
+      <TestApiProvider apis={[[starredEntitiesApiRef, mockApi]]}>
         {children}
       </TestApiProvider>
     );
   });
 
-  it('should return an empty set for when there is no items in storage', async () => {
+  it('should return an empty set', async () => {
     const { result, waitForNextUpdate } = renderHook(
       () => useStarredEntities(),
       { wrapper },
@@ -70,10 +66,11 @@ describe('useStarredEntities', () => {
     expect(result.current.starredEntities.size).toBe(0);
   });
 
-  it('should return a set with the current items when there are items in storage', async () => {
+  it('should return a set with the current items', async () => {
     const expectedIds = ['i', 'am', 'some', 'test', 'ids'];
-    const store = mockStorage?.forBucket('starredEntities');
-    await store?.set('entityRefs', expectedIds);
+    for (const id of expectedIds) {
+      mockApi.toggleStarred(id);
+    }
 
     const { result, waitForNextUpdate } = renderHook(
       () => useStarredEntities(),
diff --git a/plugins/catalog/api-report.md b/plugins/catalog/api-report.md
index bd5edcbfa6..f314932b9a 100644
--- a/plugins/catalog/api-report.md
+++ b/plugins/catalog/api-report.md
@@ -13,10 +13,13 @@ import { ExternalRouteRef } from '@backstage/core-plugin-api';
 import { IconComponent } from '@backstage/core-plugin-api';
 import { IndexableDocument } from '@backstage/search-common';
 import { InfoCardVariants } from '@backstage/core-components';
+import { Observable } from '@backstage/types';
 import { Overrides } from '@material-ui/core/styles/overrides';
 import { default as React_2 } from 'react';
 import { ReactNode } from 'react';
 import { RouteRef } from '@backstage/core-plugin-api';
+import { StarredEntitiesApi } from '@backstage/plugin-catalog-react';
+import { StorageApi } from '@backstage/core-plugin-api';
 import { StyleRules } from '@material-ui/core/styles/withStyles';
 import { TableColumn } from '@backstage/core-components';
 import { TableProps } from '@backstage/core-components';
@@ -170,6 +173,15 @@ export interface DefaultCatalogPageProps {
   initiallySelectedFilter?: UserListFilterKind;
 }
 
+// @public
+export class DefaultStarredEntitiesApi implements StarredEntitiesApi {
+  constructor(opts: { storageApi: StorageApi });
+  // (undocumented)
+  starredEntitie$(): Observable<Set<string>>;
+  // (undocumented)
+  toggleStarred(entityRef: string): Promise<void>;
+}
+
 // @public (undocumented)
 export interface DependencyOfComponentsCardProps {
   // (undocumented)
diff --git a/plugins/catalog/package.json b/plugins/catalog/package.json
index f7800af139..6179cf6c44 100644
--- a/plugins/catalog/package.json
+++ b/plugins/catalog/package.json
@@ -44,6 +44,7 @@
     "@backstage/plugin-catalog-react": "^0.7.0",
     "@backstage/search-common": "^0.2.4",
     "@backstage/theme": "^0.2.15",
+    "@backstage/types": "^0.1.2",
     "@material-ui/core": "^4.12.2",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.57",
@@ -51,7 +52,8 @@
     "lodash": "^4.17.21",
     "react-helmet": "6.1.0",
     "react-router": "6.0.0-beta.0",
-    "react-use": "^17.2.4"
+    "react-use": "^17.2.4",
+    "zen-observable": "^0.8.15"
   },
   "peerDependencies": {
     "@types/react": "^16.13.1 || ^17.0.0",
diff --git a/plugins/catalog/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.test.ts b/plugins/catalog/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.test.ts
new file mode 100644
index 0000000000..2a3c4d83ed
--- /dev/null
+++ b/plugins/catalog/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.test.ts
@@ -0,0 +1,95 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { MockStorageApi } from '@backstage/test-utils';
+import { DefaultStarredEntitiesApi } from './DefaultStarredEntitiesApi';
+import { performMigrationToTheNewBucket } from './migration';
+
+jest.mock('./migration');
+
+function getStarred(api: DefaultStarredEntitiesApi) {
+  return new Promise((resolve, reject) => {
+    const subscription = api.starredEntitie$().subscribe({
+      next(starred) {
+        resolve(starred);
+        subscription.unsubscribe();
+      },
+      error: reject,
+    });
+  });
+}
+
+describe('DefaultStarredEntitiesApi', () => {
+  beforeEach(() => {
+    (performMigrationToTheNewBucket as jest.Mock).mockResolvedValue(undefined);
+  });
+
+  afterEach(() => {
+    jest.resetAllMocks();
+  });
+
+  describe('constructor', () => {
+    it('should call migration', () => {
+      const api = new DefaultStarredEntitiesApi({
+        storageApi: MockStorageApi.create(),
+      });
+      expect(performMigrationToTheNewBucket).toBeCalledTimes(1);
+      expect(api).toBeDefined();
+    });
+  });
+
+  it('should notify and toggle starred entities', async () => {
+    const entityRef = 'component:default/mock';
+
+    const storageApi = MockStorageApi.create();
+    const storageBucket = storageApi.forBucket('starredEntities');
+    const api = new DefaultStarredEntitiesApi({ storageApi });
+
+    const values = new Array<Set<string>>();
+    api.starredEntitie$().subscribe({
+      next: value => {
+        values.push(value);
+      },
+    });
+
+    await expect(getStarred(api)).resolves.toEqual(new Set());
+
+    await api.toggleStarred(entityRef);
+    await expect(getStarred(api)).resolves.toEqual(new Set([entityRef]));
+    expect(storageBucket.snapshot('entityRefs')).toEqual(
+      expect.objectContaining({ presence: 'present', value: [entityRef] }),
+    );
+
+    await api.toggleStarred(entityRef);
+    await expect(getStarred(api)).resolves.toEqual(new Set());
+    expect(storageBucket.snapshot('entityRefs')).toEqual(
+      expect.objectContaining({ presence: 'present', value: [] }),
+    );
+
+    expect(values).toEqual([new Set(), new Set([entityRef]), new Set()]);
+  });
+
+  it('should read starred entities from storage', async () => {
+    const entityRef = 'component:default/mock';
+
+    const storageApi = MockStorageApi.create();
+    const storageBucket = storageApi.forBucket('starredEntities');
+    storageBucket.set('entityRefs', [entityRef]);
+    const api = new DefaultStarredEntitiesApi({ storageApi });
+
+    await expect(getStarred(api)).resolves.toEqual(new Set([entityRef]));
+  });
+});
diff --git a/plugins/catalog-react/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.ts b/plugins/catalog/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.ts
similarity index 90%
rename from plugins/catalog-react/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.ts
rename to plugins/catalog/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.ts
index 46a8e63084..e9cf84f11b 100644
--- a/plugins/catalog-react/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.ts
+++ b/plugins/catalog/src/apis/StarredEntitiesApi/DefaultStarredEntitiesApi.ts
@@ -15,10 +15,10 @@
  */
 
 import { StorageApi } from '@backstage/core-plugin-api';
+import { StarredEntitiesApi } from '@backstage/plugin-catalog-react';
 import { Observable } from '@backstage/types';
 import ObservableImpl from 'zen-observable';
 import { performMigrationToTheNewBucket } from './migration';
-import { StarredEntitiesApi } from './StarredEntitiesApi';
 
 /**
  * Default implementation of the StarredEntitiesApi that is backed by the StorageApi.
@@ -64,17 +64,13 @@ export class DefaultStarredEntitiesApi implements StarredEntitiesApi {
     return this.observable;
   }
 
-  isStarred(entityRef: string): boolean {
-    return this.starredEntities.has(entityRef);
-  }
-
   private readonly subscribers = new Set<
     ZenObservable.SubscriptionObserver<Set<string>>
   >();
 
   private readonly observable = new ObservableImpl<Set<string>>(subscriber => {
     // forward the the latest value
-    subscriber.next(this.starredEntities);
+    subscriber.next(new Set(this.starredEntities));
 
     this.subscribers.add(subscriber);
     return () => {
@@ -84,7 +80,7 @@ export class DefaultStarredEntitiesApi implements StarredEntitiesApi {
 
   private notifyChanges() {
     for (const subscription of this.subscribers) {
-      subscription.next(this.starredEntities);
+      subscription.next(new Set(this.starredEntities));
     }
   }
 }
diff --git a/plugins/catalog/src/apis/StarredEntitiesApi/index.ts b/plugins/catalog/src/apis/StarredEntitiesApi/index.ts
new file mode 100644
index 0000000000..42dc977fb6
--- /dev/null
+++ b/plugins/catalog/src/apis/StarredEntitiesApi/index.ts
@@ -0,0 +1,17 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export { DefaultStarredEntitiesApi } from './DefaultStarredEntitiesApi';
diff --git a/plugins/catalog-react/src/apis/StarredEntitiesApi/migration.test.ts b/plugins/catalog/src/apis/StarredEntitiesApi/migration.test.ts
similarity index 100%
rename from plugins/catalog-react/src/apis/StarredEntitiesApi/migration.test.ts
rename to plugins/catalog/src/apis/StarredEntitiesApi/migration.test.ts
diff --git a/plugins/catalog-react/src/apis/StarredEntitiesApi/migration.ts b/plugins/catalog/src/apis/StarredEntitiesApi/migration.ts
similarity index 100%
rename from plugins/catalog-react/src/apis/StarredEntitiesApi/migration.ts
rename to plugins/catalog/src/apis/StarredEntitiesApi/migration.ts
diff --git a/plugins/catalog/src/apis/index.ts b/plugins/catalog/src/apis/index.ts
new file mode 100644
index 0000000000..5c7e980890
--- /dev/null
+++ b/plugins/catalog/src/apis/index.ts
@@ -0,0 +1,17 @@
+/*
+ * Copyright 2021 The Backstage Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export * from './StarredEntitiesApi';
diff --git a/plugins/catalog/src/components/CatalogPage/DefaultCatalogPage.test.tsx b/plugins/catalog/src/components/CatalogPage/DefaultCatalogPage.test.tsx
index dcf819f976..cf2eedb14c 100644
--- a/plugins/catalog/src/components/CatalogPage/DefaultCatalogPage.test.tsx
+++ b/plugins/catalog/src/components/CatalogPage/DefaultCatalogPage.test.tsx
@@ -29,9 +29,9 @@ import {
 } from '@backstage/core-plugin-api';
 import {
   catalogApiRef,
-  DefaultStarredEntitiesApi,
   entityRouteRef,
   starredEntitiesApiRef,
+  MockStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
 import {
   mockBreakpoint,
@@ -141,10 +141,7 @@ describe('DefaultCatalogPage', () => {
             [catalogApiRef, catalogApi],
             [identityApiRef, identityApi],
             [storageApiRef, storageApi],
-            [
-              starredEntitiesApiRef,
-              new DefaultStarredEntitiesApi({ storageApi }),
-            ],
+            [starredEntitiesApiRef, new MockStarredEntitiesApi()],
           ]}
         >
           {children}
diff --git a/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx b/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx
index db9835e3a3..cc05bbe2ae 100644
--- a/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx
+++ b/plugins/catalog/src/components/CatalogTable/CatalogTable.test.tsx
@@ -22,16 +22,12 @@ import {
 import { ApiProvider } from '@backstage/core-app-api';
 import {
   entityRouteRef,
-  DefaultStarredEntitiesApi,
   MockEntityListContextProvider,
   starredEntitiesApiRef,
   UserListFilter,
+  MockStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
-import {
-  MockStorageApi,
-  renderInTestApp,
-  TestApiRegistry,
-} from '@backstage/test-utils';
+import { renderInTestApp, TestApiRegistry } from '@backstage/test-utils';
 import { act, fireEvent } from '@testing-library/react';
 import * as React from 'react';
 import { CatalogTable } from './CatalogTable';
@@ -57,7 +53,7 @@ const entities: Entity[] = [
 describe('CatalogTable component', () => {
   const mockApis = TestApiRegistry.from([
     starredEntitiesApiRef,
-    new DefaultStarredEntitiesApi({ storageApi: MockStorageApi.create() }),
+    new MockStarredEntitiesApi(),
   ]);
 
   beforeEach(() => {
diff --git a/plugins/catalog/src/components/EntityLayout/EntityLayout.test.tsx b/plugins/catalog/src/components/EntityLayout/EntityLayout.test.tsx
index 78dcf855e8..c1deaf4b74 100644
--- a/plugins/catalog/src/components/EntityLayout/EntityLayout.test.tsx
+++ b/plugins/catalog/src/components/EntityLayout/EntityLayout.test.tsx
@@ -21,15 +21,14 @@ import { AlertApi, alertApiRef } from '@backstage/core-plugin-api';
 import {
   AsyncEntityProvider,
   catalogApiRef,
-  DefaultStarredEntitiesApi,
   EntityProvider,
   entityRouteRef,
   starredEntitiesApiRef,
+  MockStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
 import { permissionApiRef } from '@backstage/plugin-permission-react';
 import {
   MockPermissionApi,
-  MockStorageApi,
   renderInTestApp,
   TestApiRegistry,
 } from '@backstage/test-utils';
@@ -48,10 +47,7 @@ const mockEntity = {
 const mockApis = TestApiRegistry.from(
   [catalogApiRef, {} as CatalogApi],
   [alertApiRef, {} as AlertApi],
-  [
-    starredEntitiesApiRef,
-    new DefaultStarredEntitiesApi({ storageApi: MockStorageApi.create() }),
-  ],
+  [starredEntitiesApiRef, new MockStarredEntitiesApi()],
   [permissionApiRef, new MockPermissionApi()],
 );
 
diff --git a/plugins/catalog/src/index.ts b/plugins/catalog/src/index.ts
index fef420d6d3..662a920f8b 100644
--- a/plugins/catalog/src/index.ts
+++ b/plugins/catalog/src/index.ts
@@ -20,6 +20,8 @@
  * @packageDocumentation
  */
 
+export * from './apis';
+
 export * from './components/AboutCard';
 export * from './components/CatalogKindHeader';
 export * from './components/CatalogSearchResultListItem';
diff --git a/plugins/catalog/src/plugin.ts b/plugins/catalog/src/plugin.ts
index b4d1a61bc1..520656e921 100644
--- a/plugins/catalog/src/plugin.ts
+++ b/plugins/catalog/src/plugin.ts
@@ -19,7 +19,6 @@ import { Entity } from '@backstage/catalog-model';
 import {
   catalogApiRef,
   catalogRouteRef,
-  DefaultStarredEntitiesApi,
   entityRouteRef,
   starredEntitiesApiRef,
 } from '@backstage/plugin-catalog-react';
@@ -33,6 +32,7 @@ import {
   fetchApiRef,
   storageApiRef,
 } from '@backstage/core-plugin-api';
+import { DefaultStarredEntitiesApi } from './apis';
 import { AboutCardProps } from './components/AboutCard';
 import { DefaultCatalogPageProps } from './components/CatalogPage';
 import { DependencyOfComponentsCardProps } from './components/DependencyOfComponentsCard';
diff --git a/plugins/home/src/homePageComponents/StarredEntities/Content.test.tsx b/plugins/home/src/homePageComponents/StarredEntities/Content.test.tsx
index ccc36f6964..9087ed3605 100644
--- a/plugins/home/src/homePageComponents/StarredEntities/Content.test.tsx
+++ b/plugins/home/src/homePageComponents/StarredEntities/Content.test.tsx
@@ -13,40 +13,23 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {
-  renderInTestApp,
-  TestApiProvider,
-  MockStorageApi,
-} from '@backstage/test-utils';
+import { renderInTestApp, TestApiProvider } from '@backstage/test-utils';
 import {
   starredEntitiesApiRef,
+  MockStarredEntitiesApi,
   entityRouteRef,
-  DefaultStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
 import React from 'react';
 import { Content } from './Content';
 
 describe('StarredEntitiesContent', () => {
   it('should render list of tools', async () => {
-    const mockStorageApi = MockStorageApi.create();
-    await mockStorageApi
-      .forBucket('starredEntities')
-      .set('entityRefs', [
-        'component:default/mock-starred-entity',
-        'component:default/mock-starred-entity-2',
-      ]);
+    const mockedApi = new MockStarredEntitiesApi();
+    mockedApi.toggleStarred('component:default/mock-starred-entity');
+    mockedApi.toggleStarred('component:default/mock-starred-entity-2');
 
     const { getByText } = await renderInTestApp(
-      <TestApiProvider
-        apis={[
-          [
-            starredEntitiesApiRef,
-            new DefaultStarredEntitiesApi({
-              storageApi: mockStorageApi,
-            }),
-          ],
-        ]}
-      >
+      <TestApiProvider apis={[[starredEntitiesApiRef, mockedApi]]}>
         <Content />
       </TestApiProvider>,
       {
diff --git a/plugins/home/src/homePageComponents/StarredEntities/StarredEntities.stories.tsx b/plugins/home/src/homePageComponents/StarredEntities/StarredEntities.stories.tsx
index 2e63762369..315c0d0d16 100644
--- a/plugins/home/src/homePageComponents/StarredEntities/StarredEntities.stories.tsx
+++ b/plugins/home/src/homePageComponents/StarredEntities/StarredEntities.stories.tsx
@@ -22,8 +22,8 @@ import {
 } from '@backstage/test-utils';
 import {
   starredEntitiesApiRef,
+  MockStarredEntitiesApi,
   entityRouteRef,
-  DefaultStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
 import { Grid } from '@material-ui/core';
 import React, { ComponentType } from 'react';
@@ -44,14 +44,7 @@ export default {
     (Story: ComponentType<{}>) =>
       wrapInTestApp(
         <TestApiProvider
-          apis={[
-            [
-              starredEntitiesApiRef,
-              new DefaultStarredEntitiesApi({
-                storageApi: mockStorageApi,
-              }),
-            ],
-          ]}
+          apis={[[starredEntitiesApiRef, new MockStarredEntitiesApi()]]}
         >
           <Story />
         </TestApiProvider>,
diff --git a/plugins/home/src/templates/DefaultTemplate.stories.tsx b/plugins/home/src/templates/DefaultTemplate.stories.tsx
index ba5e1f33fd..5dc4ff61a0 100644
--- a/plugins/home/src/templates/DefaultTemplate.stories.tsx
+++ b/plugins/home/src/templates/DefaultTemplate.stories.tsx
@@ -25,8 +25,8 @@ import { wrapInTestApp, TestApiProvider, MockStorageApi} from '@backstage/test-u
 import { Content, Page, InfoCard } from '@backstage/core-components';
 import {
   starredEntitiesApiRef,
+  MockStarredEntitiesApi,
   entityRouteRef,
-  DefaultStarredEntitiesApi
 } from '@backstage/plugin-catalog-react';
 import {
   HomePageSearchBar,
@@ -57,9 +57,7 @@ export default {
             apis={[
               [
                 starredEntitiesApiRef,
-                new DefaultStarredEntitiesApi({
-                  storageApi: mockStorageApi,
-                }),
+                new MockStarredEntitiesApi(),
               ],
               [searchApiRef, { query: () => Promise.resolve({ results: [] }) }],
             ]}
@@ -153,4 +151,3 @@ export const DefaultTemplate = () => {
     </SearchContextProvider>
   );
 };
-
diff --git a/plugins/scaffolder/dev/index.tsx b/plugins/scaffolder/dev/index.tsx
index 78e6254e09..03632f434d 100644
--- a/plugins/scaffolder/dev/index.tsx
+++ b/plugins/scaffolder/dev/index.tsx
@@ -20,16 +20,12 @@ import { scmIntegrationsApiRef } from '@backstage/integration-react';
 import {
   catalogApiRef,
   starredEntitiesApiRef,
-  DefaultStarredEntitiesApi,
+  MockStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
 import React from 'react';
 import { scaffolderApiRef, ScaffolderClient } from '../src';
 import { ScaffolderPage } from '../src/plugin';
-import {
-  discoveryApiRef,
-  fetchApiRef,
-  storageApiRef,
-} from '@backstage/core-plugin-api';
+import { discoveryApiRef, fetchApiRef } from '@backstage/core-plugin-api';
 import { CatalogEntityPage } from '@backstage/plugin-catalog';
 
 createDevApp()
@@ -44,8 +40,8 @@ createDevApp()
   })
   .registerApi({
     api: starredEntitiesApiRef,
-    deps: { storageApi: storageApiRef },
-    factory: ({ storageApi }) => new DefaultStarredEntitiesApi({ storageApi }),
+    deps: {},
+    factory: () => new MockStarredEntitiesApi(),
   })
   .registerApi({
     api: scaffolderApiRef,
diff --git a/plugins/techdocs/src/home/components/DefaultTechDocsHome.test.tsx b/plugins/techdocs/src/home/components/DefaultTechDocsHome.test.tsx
index 8618c4432f..33f5e0a08a 100644
--- a/plugins/techdocs/src/home/components/DefaultTechDocsHome.test.tsx
+++ b/plugins/techdocs/src/home/components/DefaultTechDocsHome.test.tsx
@@ -23,8 +23,8 @@ import {
 import {
   CatalogApi,
   catalogApiRef,
-  DefaultStarredEntitiesApi,
   starredEntitiesApiRef,
+  MockStarredEntitiesApi,
 } from '@backstage/plugin-catalog-react';
 import {
   MockStorageApi,
@@ -73,7 +73,7 @@ describe('TechDocs Home', () => {
     [catalogApiRef, mockCatalogApi],
     [configApiRef, configApi],
     [storageApiRef, storageApi],
-    [starredEntitiesApiRef, new DefaultStarredEntitiesApi({ storageApi })],
+    [starredEntitiesApiRef, new MockStarredEntitiesApi()],
   );
 
   it('should render a TechDocs home page', async () => {