Put beef sliced in brown paper bag with flour and pepper, close and shake well; set aside.
Melt 2 tbs margarine in large skillet and saute mushrooms. Then remove and set aside.
Saute onions and garlic together in same pan, then set them aside with mushrooms.
Add remaining 2 tbs margarine to skillet and add meat. Cook, stirring until meat is just done.
Crumble the bouillon cube over meat, add dry mustard and water, Stir while bringing to a boil and simmer 2 minutes.
Add cooked onions and mushrooms, tomato sauce and sherry. Stir briefly until just beginning to simmer.
Serve over cooked noodle or rice.
