Brown beef in butter.
Add onions (white parts only, reserve green parts for garnish).
Add flour and stir.
Add broth and bring to boil while stirring.
Reduce heat to low and add mustard. Cover and simmer 1 hour.
Saute mushrooms.
5 min before serving, add mushrooms, sour cream, and white wine. Heat through and season with salt and pepper.
Serve over noodles.