Remove excess fat from the roast and slice into ½ inch thick by 2 inches long strips. Add salt and pepper.
In a large skillet, cook beef until no longer pink and add the green onions and cook for 3-5 minutes
Put the beef and onion mixture to the side of the skillet, and whisk in the flour with the meat juices.
Pour in the beef broth and mix it in thoroughly. Bring to a boil, stirring constantly.
Reduce heat and add the mustard. Let it simmer, covered, for one hour
Mix in the mushrooms, sour cream, and white wine. Simmer for 5 more minutes and serve.