2 pounds beef sirloin roast

1/2 teaspoon salt

1/2 teaspoon ground black pepper

4 ounces butter

1 medium onion, sliced

8 ounces sliced fresh portabello mushrooms

4 tablespoons all-purpose flour

1 (10.5 ounce) can condensed beef broth

1 teaspoon prepared yellow mustard

1/3 cup sour cream

1/3 cup white wine

salt and pepper to taste

Remove any fat and gristle from the roast and cut into strips 1/2 inch thick by 2 inches long. Season with 1/2 teaspoon of both salt and pepper.

In a large skillet over medium heat, melt the butter and brown the beef strips quickly, then push the beef strips off to one side. Add the onions and sliced mushrooms, cook slowly for 5 to 8 minutes, then push to the side with the beef strips.

Stir the flour into the juices on the empty side of the pan. Pour in beef broth and bring to a boil, stirring constantly. Lower the heat and stir in mustard. Cover and simmer for 1 hour or until the meat is tender.

Five minutes before serving, stir in the sour cream and white wine. Heat briefly then salt and pepper to taste.