Combine the beef, mushrooms, onions, tomato paste, broth, wine and 3 tablespoons soy sauce in the bowl of a slow cooker. 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 the sour cream, remaining 1 tablespoon soy sauce, cornstarch and black pepper; whisk into the hot meat mixture and cook an additional 30 minutes or until sauce has thickened slightly.
Serve over pasta or rice and garnish with parsley, if using.
Notes
Nutritional information is for the meat mixture only, not the pasta or rice that it's served over.
To prepare this recipe as GLUTEN FREE, be sure to use GF beef broth and soy sauce, and serve over GF pasta or rice.