Bake in a slow oven the number of potatoes required. They should all be of about the same size. When baked, take a sharp knife and cut a neat circular opening at the top of each. Then empty the potatoes with a small spoon, leaving only the skin. Rub the potatoes through a sieve into a basin and add as much butter as there is pulp. For 6 large potatoes, add 2 yolks of egg, 3 large tablespoons of cream, season with salt, pepper, a little sugar, nutmeg, and mix all thoroughly. Then mix in gradually 2 tablespoons of Parmesan cheese. Stuff the potatoes with the mixture, sprinkle with grated Parmesan, put a small pat of butter on each potato, and bake in a moderate oven for about 25 minutes.