01 - In a large mixing bowl, combine the 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 portions.
03 - For enhanced flavor and texture, sear the meatballs in batches in a lightly oiled skillet over medium-high heat, turning every 2 to 3 minutes until golden on all sides. This step is optional but highly recommended.
04 - Arrange the meatballs in a single layer at the bottom of the crockpot.
05 - In a separate bowl, whisk together the 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 in the crockpot.
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 stir gently. Cook on HIGH for an additional 10 to 15 minutes until the gravy reaches the desired consistency.
08 - Taste and adjust seasoning as needed. Serve hot over mashed potatoes, egg noodles, or steamed rice.