You're not passing anything in. You're explicitly telling the framework that, when this particular call is invoked, then return something.
ChefService chefServiceMock = mock(ChefService.class);
// some reasonable, expected entry value
List<CookbookVersion> cookbookVersions = ...;
when(chefServiceMock.listCookbookVersions()).thenReturn(cookbookVersions);
// You're not actually using the API object, so you can pass in null.
// It'd be wiser to remove it altogether.
String actual = testObject.getAllCookBooks(chefServiceMock, null);
When you're done, you'll want to ensure that it was called, so you would want to verify
the call.
// later
verify(chefServiceMock).listCookbookVersions();
Then, make sure that you verify the actual result. I've seen tests which only validate that the mocks work, but the data that was actually being generated was garbage.
Be sure that it's data you also expect to receive from your list of inputs from the API.