Boil about three good sized potatoes until tender, then press through a colander to remove stringy substance. While hot, add about 2 tablespoons of butter, 2 tablespoons of sugar, 1/2 teaspoon salt, 1 teaspoon of nutmeg. Beat into this 1 egg and 1 cup rich sweet milk. Pour into buttered baking dish and arrange marshmallows all over the top. Bake in a moderate oven about 20 minutes. Try to serve immediately as marshmallows will fall if allowed to stand very long.