Place the frozen meatballs, baby carrots, and chopped celery into your slow cooker.
In a small bowl or large measuring cup, whisk together two packets of brown gravy mix with two cups of water. Pour the cold mixture into your slow cooker and toss with the meatballs and veggies.
Sprinkle the packet of onion soup mix over top.
Slice the butter into small pieces and evenly place them over the top.
Cook on LOW for 3-4 hours, stirring half way through to ensure everything cooks evenly and the butter and seasonings are well incorporated.
Just before serving, heat up and prepare the mashed potatoes according to the package instructions. Enjoy!
