Put into a saucepan one quart of half-glaze and one-fifth pint of truffle essence. Put the pan on an open fire, and reduce its contents; while making same absorb one and one-half pints of jelly - the latter being added to the sauce in small quantities. Reduce the sauce by one-third and after the reduction, carefully taste, and rectify the seasoning if necessary; mix a little Madeira or port with the sauce, away from the fire, and strain through muslin or through a venetian-hair sieve. Stir the sauce now and then while it cools, until it is sufficiently liquid, and at the same time consistent enough to coat immersed solids evenly with a film of sauce.