1 1/2 lb. lean beef (tenderloin is best)
Salt
Pepper (freshly ground if you have it)
2 tbsp. butter
1 c. sliced fresh (or canned) mushrooms
1 med. sized onion, thinly sliced
2 tbsp. flour
2 c. beef bouillon
3 tbsp. cooking sherry
1 tsp. dry mustard
2/3 c. sour cream

Remove all fat and gristle from beef; cut with kitchen scissors into narrow strips about 2 1/2 inches long, 3/4 inch wide and 1/4 inch thick. Sprinkle strips with salt and pepper. Set aside for 2 hours in cool (not cold) place.

Melt 1 tablespoon of the butter in a heavy skillet and saute mushrooms until tender, about 10 minutes. Remove form skillet and set aside.

In same butter, saute onion until brown; remove from skillet and set aside. Add rest of butter to skillet and, when hot, put in strips of beef and sear on all sides, but leave rare. Remove beef and set aside.

Add flour and blend with butter. Slowly add the beef bouillon, stirring well to form a smooth gravy. Add next 2 ingredients and blend well. Add to sauce the beef, onions, and mushrooms. Simmer over low heat 20 minutes (or longer).

About 5 minutes before serving, add sour cream; blend. When hot, serve. Serves 6.