Boil the potatoes the day before use. Peel them and shred them with grater. Mashed potatoes mixed with finely chopped onion and egg yolks, nutmeg. The mixture do meatballs, fried. Serve with sauce. For the sauce pan heating up well, put the butter, warming up it well, put the milk which are diluted with a little water and salt, leaving a path to a return and Serve.