Boil up the trimmings of your fish with milk, pepper and salt. Strain it and add the yolks of eggs till you get a good custard. Pour the custard into a mold, and lay in it your fish, which must already be parboiled. If you have cold fish, flake it, and mix it with the custard. Put the mold in a double saucepan. Steam it for three quarters of an hour. Turn it out, and garnish with strips of lemon peel, and if you have it, sprigs of fennel.