Parmesan cheese, grated
Put the mashed potatoes into a oven proof casserole in a layer about 2 ” thick. Use 1/2 cup unwhipped cream for each 3 cups of mashed potatoes. Whip the cream. Cover the potatoes completely with the whipped cream. Sprinkle the top with grated cheese. Put the casserole in a preheated hot oven (400° F.) until golden brown on top. Serve at once.