01 - In a large mixing bowl, combine ground beef, breadcrumbs, milk, egg, chopped onion, minced garlic, Parmesan cheese, parsley, salt, and pepper. Mix gently until just incorporated, being careful not to overwork the meat.
02 - Roll the mixture into 1 1/2-inch meatballs, yielding approximately 20 to 24 uniform pieces.
03 - For enhanced flavor and texture, heat a thin layer of oil in a skillet over medium-high heat. Sear meatballs in batches for 2 to 3 minutes per side until lightly browned on all surfaces.
04 - Transfer the shaped meatballs into the crockpot in an even layer.
05 - In a separate bowl, whisk together beef broth, cream of mushroom soup, Worcestershire sauce, soy sauce, dried thyme, onion powder, and garlic powder until smooth. Pour the gravy mixture evenly over the meatballs.
06 - Cover and cook on LOW for 4 to 5 hours or on HIGH for 2 to 3 hours, until the meatballs are cooked through and tender.
07 - Stir in the heavy cream. If the gravy needs thickening, add the cornstarch slurry and cook on HIGH for an additional 10 to 15 minutes until it reaches the desired consistency.
08 - Taste and adjust seasoning as needed. Serve hot over mashed potatoes, egg noodles, or steamed rice.