Peel cooked potatoes and mash in the hot drained pan they were boiled in. Mash thoroughly and then beat fluffy adding milk for your favorite desired consistency. Season with salt and pepper.
Heap mixture in center of a greased pie plate or baking dish. Make a crater in the center the size of a custard cup.
Mix yolks, milk, butter, cheese, salt and pepper to taste. Pour into the crater. Bake in a very hot oven (450°F) until the topping browns, cracks and runs down the side of the potato volcano, about 15 minutes.