Ingredients:

1½ lb lean beef round or fillet

3 Table spoons butter

½ lb fresh mushrooms

2 medium size onions

2 Table spoons flour

2 cups beef broth

2 Table spoons tomato paste

1 tea spoon Dijon mustard

¾ cup sour cream

Salt and pepper to taste

Cut meat into strips about 2 inches long and one fifth of an inch wide. Season with salt and pepper and let it stand in cool place for 2 hours. Melt 2 Table spoons of butter in a skillet. Slice and stir fry mushrooms until tender, about 10-15 min. Set   mushrooms aside. Cut onions into small cubes and cook until golden brown. Set cooked onions aside. Melt remaining butter and add beef. Cook meat until light brown, but leave it rare. Remove meat and set aside. Blend flour into fat left from cooking meat. Little by little add beef broth, stirring it constantly, until smooth and a little thickened. Add tomato paste and mustard. Combine sauce with meat, mushrooms and onions. Cook on low flame for 20 minutes. Add sour cream and cook for 5 more minutes. Serve with steamed rise or mashed potatoes.