(To use for eggs villeroi, and for coating cold meats that are to be heated again)
Put in a saucepan the butter and onion; fry for a few moments, but not brown. Remove the onion, and add the flour; cook but do not brown the flour. Dilute with the stock, and boil, stirring constantly until the sauce is very thick. Season with the salt, pepper, cayenne and nutmeg; remove from the fire, and add the yolks beaten with the cream or milk. Place again on the fire, and let thicken until quite stiff and elastic. Do not let it boil after the eggs are added, or it will curdle; stir constantly. When it is beginning to cool pour it over the articles it is to coat, or roll the articles in it as the receipts direct. Chopped parsley, truffles, and mushrooms may be mixed with this sauce, if desired. The thick sauce left from coating the articles may be diluted with stock or milk, and served with them. This amount of sauce is sufficient to coat and to give diluted sauce for a dozen eggs villeroi.