Preheat oven to 400°.
Combine 2 tablespoons half-and-half with flour in a large bowl, stirring with a whisk. Add the remaining half-and-half, cheese, and next 5 ingredients (cheese through garlic), stirring with a whisk. Arrange half of the potato slices in a single layer in an 11 x 7-inch baking dish coated with cooking spray. Pour half of the milk mixture over potato slices, stirring the milk mixture immediately before adding. Repeat procedure with remaining potato slices and milk mixture. Bake at 400° for 1 hour and 10 minutes or until potatoes are tender and golden brown.