Beef Stroganoff - cooking recipe

Ingredients

2 1/2 to 3 lb. beef round steak (1/2-inch thick)
instant meat tenderizer (optional)
3 Tbsp. butter or margarine
1 onion, halved and thinly sliced
1 Tbsp. flour
1 c. beef bouillon
1 tsp. prepared mustard
1/2 c. sour cream or nonfat yogurt (at room temperature)
salt and pepper to taste
1 (4 oz.) can mushrooms, sliced or chopped
egg noodles

Preparation

Cut steak crosswise in 1/4-inch strips and spread out on counter or board.
Apply tenderizer, if desired.