Trim fat from beef; discard. Slice beef across prominent grain into thin slices. Cut onion lengthwise in half and slice crosswise into 1/4 inch slices.Heat the wok over medium high heat until hot. Add butter and swirl to coat the bottom. Add beef and stir fry about 2 minutes or until well browned. Remove beef to a large bowl.Reduce heat to medium.Add water, mushrooms, and onions. Stir fry about 2 minutes or until onion is tender. Add flour and mix well. Gradually stir in broth, wine and salt. Heat to boil.Reduce heat to low; simmer 5 minutes.Stir sour cream and dill weed into mushroom mixture. Return the beef and any accumulated juices to the wok; heat through. Serve over noodles, if desired. Garnish ,if desired.