In a large Crock-Pot, whisk together beef broth and condensed soup.
Add Worcestershire sauce, garlic powder, paprika, salt, and black pepper, and stir.
Place the frozen meatballs, mushrooms, and onion into the Crock-Pot, ensuring they are coated with the sauce.
Cover the Crock-Pot and cook on high for 3-4 hours.
Whisk the water and cornstarch together to make a slurry.
Stir in the slurry and mix to combine. Add the sour cream and softened cream cheese, and mix. Cover and heat until the sauce is warmed through, about 30 minutes.
Garnish with fresh parsley. Serve meatballs with sauce over noodles, rice, or mashed potatoes.