Beef Stroganoff

3/4 lb. boneless round steak
1 i-oz carton plain low-fat yogurt
2 Tbs. flour
1 Tbs. tomato paste
1 tsp. beef bouillon granules
2 tsp. Worcestershire sauce
1/2 tsp. thyme
1/4 tsp. dry mustard
2 cups sliced fresh mushrooms
1/2 cup chopped onion
1 Tbs. margarine
2 Tbs. dry white wine
2 cups hot cooked noodles

Trim fat from meat and thinly slice meat across grain into bite-size strips.
In a small bowl stir together yogurt and flour. Stir in tomato paste, bouillon granules, Worcestershire sauce, thyme, mustard, and 1/8 tsp. pepper. Set aside.
In a large skillet cook mushrooms and onion in margarine until tender, remove from skillet.
Add steak to skillet. Cook 2 to 4 minutes or until no longer pink. Remove from skillet.
Add wine and 1/3 cup water to skillet. Bring to boiling. Stir yogurt mixture into skillet. Return meat, mushrooms, and onion to skillet. Cook and stir until thickened and bubbyly. Cook 1 minute more
Serve over noodles.