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 incorporated—avoid overworking the meat to keep the meatballs tender.
02 - Roll the mixture into 1½-inch meatballs using your hands and arrange them on a large plate or baking sheet.
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 - Gently lower the formed meatballs into the gravy mixture, arranging them so they are mostly submerged in the liquid.
05 - Cover the slow cooker and cook on LOW for 6 hours or on HIGH for 3 hours, until the meatballs are cooked through and reach an internal temperature of 160°F.
06 - In a small bowl, whisk together the cornstarch and cold water to form a smooth slurry. Stir the slurry gently into the slow cooker, cover, and cook on HIGH for an additional 15 to 20 minutes until the gravy thickens to your desired consistency.
07 - Serve the meatballs and gravy hot over mashed potatoes, egg noodles, or steamed rice.