1 1/2-2 lbs. sirloin steak
2 tbsp. butter
1/2 c. onion, chopped
2 tbsp. flour
2 beef bouillon cubes
1 1/2 c. boiling water
1 tbsp. tomato paste
1 tsp. dry mustard
1 1/2 tsp. salt
Dash pepper
6 oz. jar sliced mushrooms, not drained
1/2 c. sour cream
8 oz. cooked noodles

Cut meat into strips. Brown meat in butter in heavy fry pan, turning to brown on all sides. Remove meat; add onion and cook over medium heat until clear. Blend in flour, cooking until it browns lightly.

Slowly stir in bouillon cubes (dissolved in boiling water). Continue cooking until slightly thickened. Add tomato paste, seasonings, mushrooms and meat. Cover and simmer over low heat 30-35 minutes or until meat is tender. Fold in sour cream. Cook, do not boil, until heated through. Serve over cooked noodles or rice.