Grate the potatoes and mash them through a sieve, if you use them raw. If you use the cold boiled Potatoes, simply mash them. Beat the butter and the sugar to a rich cream, and add the well-beaten yolks of the eggs, and then add the grated Potatoes and the spices, and finally the whites of the eggs, beaten to a stiff froth. Mix all well. Add the liquors. Turn into a buttered baking pan, and let the Pudding bake in a moderate oven for three-quarters of an hour. The addition of the liquors is optional. Serve hot or cold, with a Cream Sauce.