Add water and seasoning mix. Stir to loosen browned bits from pan. Transfer meat and drippings to a 3-quart slow cooker.
SautÃƒÂ© mushrooms and onion in butter until tender. Combine the wine, mustard and sugar, stir into mushroom mixture. Add to slow cooker. Cover and cook on low for 6-8 hours or until meat is tender.
Stir in sour cream. Serve with noodles. Sprinkle with parsley if desired.