This rich, classic sauce is flavored with Madeira and pungent, earthy black truffles, which are a specialty of Périgueux, a city in the Perigord region of southwestern France. Julia Child recommended Sauce Périgueux for "filet of beef, fresh foie gras, veal, egg dishes, and timbales," all delicous ways to enjoy the luxury of truffles.
Bring the reconstituted Demi-Glace Gold® to a simmer over low heat in a small saucepan. Add the truffles, brining liquid, and Madeira and simmer for 1-2 minutes.
Whisk in the butter and season to taste with salt and pepper.
Black truffles preserved in brine and packaged in cans or jars can be found at many gourmet and specialty food markets.