1. Add the frozen fully cooked meatballs to the bottom of a 6 quart or larger slow cooker.

2. Scatter the baby carrots and sliced celery evenly over the meatballs so they are distributed throughout the pot.

3. In a medium bowl, whisk together the beef broth, brown gravy mix packets, onion soup mix, Worcestershire sauce, soy sauce, garlic powder, onion powder, dried parsley, dried thyme, and black pepper until smooth and well combined.

4. Pour the gravy mixture evenly over the meatballs and vegetables, making sure everything is coated in the sauce.

5. Cover the slow cooker and cook on LOW for 4 to 6 hours, or on HIGH for 2 to 3 hours, until the vegetables are tender and the meatballs are heated all the way through.

6. If you prefer a thicker gravy, stir together the cornstarch and water in a small bowl, then stir the slurry into the hot liquid in the slow cooker. Cover and cook on HIGH for an additional 10 to 15 minutes, or until the gravy has thickened to your liking.

7. Taste the gravy and adjust the seasoning if needed, adding a bit more black pepper or a pinch of salt if you like.

8. To serve, spoon a generous amount of warm mashed potatoes onto each plate, then top with meatballs, carrots, celery, and plenty of gravy. Serve immediately and enjoy.