Preheat broiler. In extra large skillet brown ground beef over medium-high heat; drain off fat & set aside. In the same skillet, add onions with a little olive oil & cook until transparent. Stir onions occasionally.
Place cooked beef back into the pan with the cooked onions, long with the soup, frozen vegetables, worcestershire sauce, salt & pepper. Cook until heated through. If it is too thick add water or beef broth to get it to the thickness you want but not too runny. Stir in half the cheese.
Divide meat mixture between 4 16oz broiler safe dishes that have been sprayed with Pam. Top with prepared mashed potatoes & sprinkle with remaining cheese. Broil 3 inches for broiler for 3 to 4 minutes. Remove from broiler & if you want garnish with chopped parsley.
You can substitute with ground turkey or chicken, too. I change soup to cream of chicken instead of tomato soup.