Add water and seasoning mix. Stir to loosen browned bits from pan. Transfer meat and drippings to a 3-quart slow cooker.
Sauté 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.
