1 1/4 lb. flank, strip loin, rib eye or sirloin steak
4 to 5 tsp. vegetable oil 
2 cups onions, chopped 
1 lbs. mushrooms, sliced, (about 4 cups)
1 1/2 cups chicken stock
4 tbsp. tomato paste
2 tbsp. Dijon mustard
1/2 tsp. Worcestershire sauce
2 tsp. sugar (optional)
2 to 4 tbsp. whipping cream or regular sour cream
1/2 cup chopped fresh parsley

Preparation Time 15 minutes

Makes 4 Servings

1. Remove fat from steak and discard. Slice into 1/4" strips. If using flank steak, slice across grain. Heat 2 teaspoons oil in a nonstick frying pan set over medium high to high heat. Brown meat a few slices at a time and remove from pan. Meat should be slightly rare. Add oil as needed. When all meat has been browned and removed from pan, add onions. Sauté until transparent, about 10 minutes. If pan becomes dry, add 1/4 cup water

2. Add mushrooms and cook just until they're releasing their juices, about 5 minutes. Add stock, tomato paste, mustard, Worcestershire sauce, salt and pepper to taste. Scrape bottom of pan to get up browned bits. Boil gently, reducing heat if necessary and stirring often, until sauce is slightly thickened, from 8 to 10 minutes. 

3. Taste. Add sugar, more mustard or Worcestershire sauce, if you wish. Add browned meat and stir in cream. Continue to cook just until meat is hot, from 2 to 3 minutes. Serve over hot buttered egg noodles and sprinkle with parsley.