1. Preheat oven to 375°.
2. Rub a broiler-safe 11 x 7-inch baking dish with garlic; discard garlic. Coat dish with butter. Combine milk and next 5 ingredients (through potatoes) in a skillet; bring to a simmer. Cook 8 minutes or until potatoes are almost tender. Spoon potato mixture into prepared baking dish. Sprinkle with cheeses. Bake at 375° for 35 minutes.
3. Preheat broiler. Broil 3 minutes or until golden. Let stand 10 minutes.