Arrange 1/2 of the potato slices in baking dish. In small bowl, mix Alfredo sauce, milk and 2 tablespoons of the fennel leaves. Pour 1/2 of sauce mixture over potatoes in dish; top with 1 cup Swiss cheese. Spoon chicken mixture evenly over cheese. Top with remaining potatoes; press to make mixture flat. Pour remaining sauce mixture over top. Sprinkle with remaining 1 cup Swiss cheese.