2 lbs. thin Sirloin strips
2 c. mushrooms, sliced
2 med. onions, sliced
2 tbsp. oil
2 cubes or tsp. beef bouillon
1 c. hot water
1/2 tsp. salt
2 tbsp. tomato paste or ketchup
1 tsp. dry or prepared mustard
2 tbsp. flour
1/2 c. water
1/2 to 1 c. sour cream

Brown steak strips, onion, and mushrooms in hot oil until golden brown. Add bouillon, hot water, salt, tomato paste, and mustard. Cover and simmer about 30 minutes or until tender. Combine flour and remaining water. Stir into meat mixture. Bring to a boil, stirring constantly. Reduce heat. Stir in sour cream. Simmer, but do not boil. Serve over rice or noodles.