Add frozen meatballs to your crockpot. Top with sliced onions, butter, and season with garlic powder, onion powder, smoked paprika, black pepper, and thyme.
Add Worcestershire sauce, minced garlic, French onion soup, and low sodium beef broth.
Cook on low for 4-6 hours. Stir a few times while the meatballs cook.
For thicker gravy you can add a cornstarch slurry. Mix 1 tbsp cornstarch with 1 tbsp cold water. Stir this into the slow cooker. This will thicken while you cook the egg noodles.
If serving over egg noodles, boil a package following the directions on the package.
Top meatballs with shredded mozzarella cheese and let sit in the crockpot until melted. Serve over egg noodles, mashed potatoes, or rice. Top with dried parsley. Enjoy!