Preheat oven to 325 F. Generously grease gratin dish with butter. Layer the potatoes, cheese, garlic, and seasonings in the dish, ending with the potatoes. Pour the milk over the top. Sprinkle 2 tablespoons of Gruyere cheese over the top. Dot the top with butter. Bake for 1 1/2 hours, or until the potatoes are done. If the top is not brown enough, put the dish under a hot broiler for 1 or 2 minutes.{$7e}(Original recipe for 5)