In a pot of boiling water, cook macaroni for 5-6 minutes or until almost al dente. Drain and transfer to a 5-quart crockpot.
In a large skillet, cook and stir ground beef and beef stew seasoning mix, until beef is browned, breaking up clumps. Drain off fat. Stir beef, cheese, sou, onion and beef broth into pasta in crockpot.
Cover and cook on LO heat for 2-4 hours.
Serve with chopped tomato and parsley, if desired.