Cut steak into 1/4-inch strips. Coat with salt and pepper. Put into bottom of slow-cooking pot or crockpot with onion.
Mix garlic, Worcestershire sauce, bouillon and catsup. Pour over meat. Cover and cook on low for 6 to 8 hours.
Turn control to high. Add mushrooms.
Dissolve flour in small amount of water. Add to meat mixture, stirring until blended. Cook on high for 15 minutes or until slightly thickened. Stir in sour cream. Turn off. Serve with rice or noodles.Servings: 6