- Trim all excess fat from steak and cut meat into 3" strips about 1/2" wide.
- Combine 1/2 cup flour, salt, pepper and dry mustard; toss with the steak strips to coat thoroughly.
- Place coated strips in crock pot; stir in onion rings and mushrooms.
- Add beef broth and the wine or water; stir well.
- Cover and cook on low setting for 8-10 hours.
- Before serving, combine sour cream with 1/4 cup flour; stir into crock pot. Serve over hot buttered noodles or fluffy rice. 8 servings (approx 3 quarts).