Remove excess fat from the roast and slice into ½-inch thick by 2-inch long strips. Add salt and pepper.
In a large skillet, melt the butter and cook the beef until no longer pink. Add the green onions and cook for 3-5 minutes
Put the beef and onion mixture to the side of the skillet, and whisk the flour into the meat juices.
Pour in the beef broth and mix it in thoroughly. Bring to a boil, stirring constantly.
Reduce the 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. Check the seasoning and add more salt if needed. Serve. over egg noddles.