In a large mixing bowl, gently combine the ground beef, breadcrumbs, Parmesan cheese, egg, garlic powder, finely chopped onion, salt, and black pepper. Be careful not to overmix, as this can make the meatballs tough.
Once the mixture is well-combined, shape it into meatballs roughly an inch in diameter. Using wet hands can help prevent sticking.
Place the meatballs in your crock pot, ensuring they are evenly distributed.
Pour the French onion soup over the meatballs, ensuring they are well-coated.
Secure the lid on your crock pot and set it to cook on low for 6-8 hours or on high for 3-4 hours. The low-and-slow method is preferred for maximum flavor.
About 30 minutes before the cooking time is up, carefully remove the lid and sprinkle the shredded mozzarella cheese over the meatballs.
Replace the lid and allow the cheese to melt into a gooey, delightful topping.
Once cooking is complete, serve the meatballs warm, garnished with fresh herbs if desired.
