Philly Cheese Steak Casserole

1 lb beef boneless sirloin steak, about 3/4 inch thick

1/4 teaspoon pepper

2 medium onions, chopped (1 cup)

1 small green bell pepper, chopped (1/2 cup)

1 3/4 cups Progresso® beef flavored broth (from 32-oz carton)

1/4 cup Gold Medal® all-purpose flour

1/2 cup fat-free half-and-half

1 tablespoon Dijon mustard

3/4 cup shredded reduced-fat Cheddar cheese (3 oz)