In a large mixing bowl, combine the ground beef, ground pork, breadcrumbs, Parmesan cheese, minced garlic, parsley, egg, salt, and pepper until well incorporated.

Using your hands, shape the mixture into meatballs about 1 to 1.5 inches in diameter.

If desired, place meatballs on a baking sheet and broil for about 5 minutes for a crispy exterior.

Pour the marinara sauce into the bottom of the crockpot.

Carefully place the meatballs into the crockpot, ensuring they are nestled in the sauce.

Cover and cook on low for 6 hours.

If possible, stir the meatballs gently halfway through cooking.

Once cooked, serve the meatballs with the sauce over pasta, in a sub, or on their own.