Ingredients for 4 servings:
1. 2 lbs lean boneless sirloin (trimmed of fat and gristle) or 2 lbs bottom round steaks, in one piece (trimmed of fat and gristle)
2. 2 teaspoons salt
3. 1/2 teaspoon fresh ground pepper
4. 4 tablespoons butter
5. 1 medium onion, thinly sliced
6. 1 tablespoon flour
7. 1 teaspoon mustard powder (OR 1 Tablespoon prepared Dijon style mustard)
8. 1/2 cup dry white wine
9. 2 teaspoons tomato paste
10. 1 tablespoon minced onion
11. 1/2 lb mushroom, thinly sliced
12. 2 tablespoons dry white wine
13. 1 cup sour cream, warmed

Directions:
1. Cut meat into 1/2 inch thick slices. Place between sheets of waxed paper and pound until its 1/4 inch thick (be careful not to tear meat). Cut pounded meat into 2×1/2 inch slices. Sprinkle meat with salt and pepper, let stand for 15 minutes.
2. Heat 2 TBS butter in a frying pan large enough to hold everything. Add sliced onion, cook over medium heat for 5 minutes.
3. Add meat to pan and cook for 3 minutes, turning meat to brown evenly.
4. Stir in flour and mustard, and cook 1 minute more. Add 1/2 cup wine and optional tomato paste. Reduce heat to low, cover pan and simmer for 5-10 minutes, stirring frequently.
5. In another frying pan, heat 2 TBS butter. Add minced onion and mushrooms. Cook over medium heat 2 minutes. Add 2 TBS wine and cook 2 minutes more. Add mushroom mixture to meat mixture. Check seasonings and add warmed sour cream.
6. Over lowest possible heat, simmer for 5 minutes to heat through. Do NOT let it boil.
7. Serve over hot rice with a green vegetable on the side.