In a large bowl, combine the ground beef, breadcrumbs, Parmesan cheese, egg, garlic powder, onion powder, dried thyme, salt, and pepper. Mix well until all ingredients are combined.
Form the beef mixture into 1-inch meatballs and place them in the slow cooker.
In a separate bowl, whisk together the beef broth, ketchup, Worcestershire sauce, and soy sauce. Pour this sauce over the meatballs in the slow cooker.
Cover the slow cooker with a lid and cook on low for 6 hours, or on high for 3 hours, until the meatballs are cooked through and tender.
After cooking, mix the cornstarch with water in a small bowl to create a slurry. Stir this mixture into the sauce in the slow cooker to thicken it slightly. Let cook for an additional 15 minutes on high.
Serve the meatballs hot, drizzled with sauce, and garnish with chopped parsley.