Though you can follow this procedure with almost any tender cut of beef (and with chicken breasts, if that direction appeals to you), it's a perfect treatment for tenderloin medallions (filet mignon).
03Keeping mixture at a steady simmer, return meat and accumulated juices to pan. Cook, turning two or three times, until meat is done to your liking (125 degrees internal temperature for medium-rare). Remove to a plate, and add lemon juice, if using, salt and pepper to the sauce as needed. Spoon sauce over meat, garnish with chives or parsley, and serve.