This traditional French casserole of thinly sliced potatoes with milk, cream, garlic, and Gruyere cheese, takes a little effort, but the result is a bubbling, indulgent accompaniment to a special meal.
Preheat oven to 400 degrees, with rack in center. Generously butter a 9-by-12-inch glass baking dish. Peel potatoes, and slice into 1/8-inch-thick rounds. Place slices in a bowl of cold water as you go to prevent discoloration.
In a medium saucepan, combine garlic, milk, heavy cream, salt, nutmeg, and bay leaf. Bring just to a simmer over medium heat, and pour into prepared baking dish. Discard bay leaf.
Drain potatoes in a colander, and transfer to baking dish. Using a large spoon, toss potatoes with milk mixture pressing down gently to distribute the potato slices evenly. Season with pepper. Dot with butter, distributing evenly over entire surface; sprinkle with cheese.
Place in oven; bake until potatoes can be pierced with a fork and top is brown, 45 to 50 minutes. Serve immediately.