Thick slice into large saut pan. Add butter and saut on medium heat, stirring constantly. Thinly slice shallots, add to pan and saut 3-4 minutes. Turn heat to high, add sherry or brandy and saut until 90% of sherry is evaporated. Add beef broth and reduce by half. This recipe can be easily adapted for a pasta sauce by adding 2/3 cup heavy cream to mixture after broth is reduced. Lower heat to medium high and stir constantly until desired thickness is obtained. Season with fresh or dried tarragon and fresh ground pepper. Hint: Sherry goes better as a pasta sauce.