In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, Parmesan cheese, parsley, eggs, garlic powder, onion powder, salt, and black pepper. Mix well until all ingredients are evenly incorporated.
Shape the mixture into meatballs, about 1-2 inches in diameter. You should get around 24 meatballs.
For added flavor, you can brown the meatballs on a baking sheet under the broiler for 4-5 minutes, turning once until lightly browned. This step is optional but enhances the flavor and texture.
Place the uncooked (or browned) meatballs into the Crock Pot.
Pour the French onion soup over the meatballs, ensuring they are well covered.
Cover the Crock Pot and cook on low for 6 hours or until the meatballs are cooked through and tender.
About 15 minutes before serving, sprinkle the Swiss cheese over the meatballs and cover again until melted.
Serve the meatballs warm, garnished with additional parsley if desired.