1-lb. whole lamb tenderloin (from saddle) 1/2 cup red currant jelly, melted 4 tablespoons (1/2-stick)-butter 1/2 cup fresh black currants Boil wine and shallots in heavy small saucepan until liquid is reduced to 2 tablespoons. Add stock and cassis and boil until reduced to 3/4 cup. Strain sauce. Season with salt and pepper. keep warm over low heat. Preheat grill or broiler. Brush both sides of lamb very lightly with jelly. Grill lamb 3 minutes on each side for medium-rare. Slice lamb and arrange on plates. Whisk butter into sauce 1 tablespoon at a time. Stir in currants. Spoon sauce over lamb and serve.