Combine beef, mushrooms, onions, tomato paste, broth, wine and 3 tablespoons of the soy sauce in slow cooker bowl. Cover and cook on HIGH for 4 hours or on LOW for 6 hours or until beef is tender.
In a small bowl, stir together sour cream, remaining 1 tablespoon soy sauce, cornstarch and black pepper; whisk into slow cooker bowl and cook an additional 30 minutes or until sauce has thickened. Serve over egg noodles and sprinkle with parsley, if desired.
