Petite Rolls with Lamb, Mushrooms and Red Onions

YIELD: 24 servings

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

1. 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.
2. 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.
3. 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.
4. 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.

Photo and recipe from the American Lamb Board.