1 lamb top round(1 to 11/4 lbs.) 1/2 cup prepared balsamic dressing 1 tsp. Dijon-style mustard 1/2 tsp. coarse ground pepper 24 medium Portobello mushrooms, stems removed 1/4 cup, 2 Tbsps. olive oil, divided 1/4 cup balsamic vinegar 1 large red onion, sliced in thin rings 24 rolls petite-size, sliced 48 strips roasted red bell pepper, 2" long
FOR THE LAMB: Trim off all visible fat from lamb. In a bowl, blend dressing, mustard and pepper. Pour over meat and marinate in refrigerator for 4 hours. Remove lamb from marinade and roast in 325°F oven for 50 to 60 minutes or until desired degree of doneness. Remove from oven, cover and let stand for 10 minutes. Thinly slice, cover and refrigerate.
FOR THE VEGETABLES: Place mushrooms on pan. In small bowl, whisk together 1/4 cup oil and vinegar. Brush all sides and centers of mushroom with mixture. Bake in 375°F oven for 15 minutes. Remove and cool.
In large skillet, heat remaining 2 Tbsps. olive oil over medium-high heat. Add onion rings and sautè for 6 to 8 minutes, until lightly browned. Set aside and cool.
FOR EACH MINI SANDWICH: Place a mushroom on base of roll and lay on two bell pepper strips. Top with sliced lamb and a few onion rings.
YIELD: 24 servings