01 -
Place frozen beef meatballs in a single layer at the bottom of a 4-6 quart slow cooker.
02 -
Pour the can of French onion soup over the meatballs, then sprinkle the beefy onion soup mix evenly on top.
03 -
Pour in the beef broth. Cover and cook on high for 2 to 3 hours or on low for 5 to 6 hours.
04 -
In a small bowl, whisk together cold water and cornstarch until smooth to create a slurry.
05 -
Stir the slurry into the slow cooker mixture, combine thoroughly, then re-cover and cook for an additional 10 minutes.
06 -
Sprinkle shredded mozzarella cheese over the meatballs, cover, and cook until the cheese is melted.
07 -
Serve warm over mashed potatoes or egg noodles with a side of steamed green beans, garnished with fresh thyme if desired.