1. Heat oven to 325 degrees F. In a large saucepan, combine sliced potatoes and milk, and place over high heat. Bring to a boil, then reduce heat to low; cover, and simmer until potatoes just begin to get tender, about 3 minutes.
2. Meanwhile, grate cheese and set aside. Place a colander over a large bowl, and drain potatoes, reserving milk. (You should have 2 cups of thick, starchy milk. If potatoes have absorbed more than 1 cup of milk, add enough milk to bring the reserved milk volume to 2 cups.)
3. Rub a 3 1/2-quart oval casserole with garlic and butter. Arrange sliced potatoes in the casserole in two layers, and season with salt and pepper to taste. Dot with remaining butter and pour in the reserved cooking milk and cream. Scatter grated cheese over the top.
4. Place casserole in the lower third of the oven, and bake until the cheese has turned deep golden brown and the milk has reduced and thickened, 80 to 90 minutes. Remove from oven, and serve immediately.

Yield: 14 servings