Yes there is a way to make N calls with WillReturn and then CallOriginal:
[Test, Isolated]
public void TestMockSome()
{
MockSome ms= new MockSome();
Isolate.WhenCalled(()=>ms.ReturnTen()).WillReturn(11));
//This is how to mock so that subsequent calls are real call
Isolate.WhenCalled(()=>ms.ReturnTen()).CallOriginal());
Assert.AreEqual(11, ms.ReturnTen());
Assert.AreEqual(10, ms.ReturnTen());
}
And you can use WillReturnRecursiveFakes as well