Three tablespoonfuls vinegar, 1 lb. butter, yolks of 2 eggs, pepper and salt.

Put 3 tablespoonfuls vinegar in a saucepan, and reduce it on the fire to a third; add 1/4 lb. butter and the yolks of 2 eggs. Place the saucepan on a slow fire, stir the contents continuously, and as fast as the butter melts add more, until 1 lb. is used. If the sauce becomes too thick at any time during the process, add a tablespoonful of cold water and continue stirring. Then put in pepper and salt to taste, and take great care not to let the sauce boil. When it is made-that is, when all the butter is used and the sauce is of the proper thickness-put the saucepan containing it into another filled with warm (not boiling) water until the time of serving.