Boil two calf's feet in two quarts of water, till the liquid is reduced one half, and the meat has dropped to pieces. Then strain it into a deep dish or pan, and set it by to get cold. When it has congealed, take all the fat carefully off; put a tea-cupful of the jelly into a sauce-pan, and set it on hot coals. When it has nearly boiled, stir in by degrees the beaten yolk of an egg, and then take it off immediately. You may add to it a little sugar, and some grated lemon-peel and nutmeg.