Season beef with desired amount of salt and pepper and place in slow cooker; top with chopped onion.
Add golden mushroom or cream of mushroom soup, mushrooms, garlic, Worcestershire, 1/4 cup water, and beef bouillon.
Mix together flour and beef broth in a small bowl; pour over beef.
Cover and cook on low 6 - 7 hours.
Stir in sour cream and parsley and cook 1 more hour.
Serve over egg noodles, if desired.