Add the whipped yolks of six eggs to six tablespoonfuls of boiling vinegar. Pour into a tin pail, set in a pan of boiling water, and stir until quite stiff. Remove from the fire, add four tablespoonfuls of butter, and beat until perfectly mixed. When cold season to taste with salt, pepper, mustard, etc., and thin with oil to the required consistency. This will keep several days in a cold, dark place.