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 - Heat a thin layer of oil in a large skillet over medium-high heat. Sear meatballs in batches for 2 to 3 minutes per side until lightly browned. This step builds depth of flavor and improves texture but can be skipped to save time.
04 - Arrange the meatballs in a single layer at the bottom of the crockpot.
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 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 reach an internal temperature of 160°F.
07 - Stir in the heavy cream. If the gravy is too thin, blend the cornstarch slurry into the crockpot, then cook on HIGH for an additional 10 to 15 minutes until the sauce thickens to your preferred consistency.
08 - Taste and adjust seasoning with salt and pepper as needed. Serve hot over mashed potatoes, egg noodles, or steamed rice.