01 - In a large mixing bowl, combine ground beef, ground pork, breadcrumbs, milk, egg, finely chopped onion, minced garlic, salt, pepper, oregano, and parsley. Mix gently until just combined, being careful not to overwork the meat.
02 - Shape the mixture into uniform 1½-inch meatballs and arrange them on a large plate or tray.
03 - In the slow cooker insert, whisk together beef broth, cream of mushroom soup, Worcestershire sauce, Dijon mustard, onion powder, garlic powder, salt, and pepper until smooth and well blended.
04 - Carefully place the formed meatballs into the gravy mixture, ensuring they are mostly submerged in the liquid.
05 - Cover and cook on LOW for 6 hours or on HIGH for 3 hours, until the meatballs are cooked through and tender.
06 - If a thicker gravy is desired, whisk together cornstarch and cold water in a small bowl to create a slurry. Stir the slurry gently into the slow cooker, cover, and cook on HIGH for an additional 15 to 20 minutes until the gravy reaches the desired consistency.
07 - Serve the meatballs and gravy hot over mashed potatoes, egg noodles, or steamed rice.