Boil dry, mealy potatoes, peel and set in the oven to dry, but do not let them get hard. Rub through a colander, or grate, or rub through a vegetable-press into a mealy mass. Beat with a silver or wooden spoon to a cream with hot milk in which a lump of butter has been melted. Season with salt and pepper, pour into a pudding-dish and bake, covered, in a quick oven until it begins to brown. Wash over with egg and leave in the oven one minute longer. Serve at once.