2 lbs. sirloin tip of beef (1/2" thick, 1/2" wide)
1/2 c. finely chopped onion
2 tbsp. butter
2 tbsp. flour
2 bouillon cubes
1/2 c. sour cream
2 tbsp. tomato paste
1 tsp. dry mustard
1 1/2 tsp. salt
Dash of pepper
1 (4 oz.) can mushrooms
1 1/2 c. water

Cook meat in butter, brown quickly; remove. Add onion to butter and cook until clear. Blend in flour, cook until brown. Stir in bouillon cubes dissolved in the water, cook until thickened. Add tomato paste, seasonings, mushrooms and meat. Cover and simmer 30 minutes (until meat is tender). Fold in sour cream and cook until heated through. Serve over cooked noodles.