Preheat your oven to 400 degrees F. Add onion, carrot, celery, garlic, egg , bread crumbs and seasonings to a large bowl then stir with a fork to combine. Add ground chicken then mix until combined (do not over mix or meatballs will be tough). Divide chicken mixture into quarters, then each quarter into 6 balls. Leaving you with 24 balls.
Place meatballs onto a sprayed cooling rack set on top of a baking sheet, then bake for 20 minutes.
Melt butter in a large skillet over medium heat then add buffalo wing sauce, and italian dressing mix. Stir to combine. Add cooked meatballs to skillet then use a spoon to coat in sauce. Place a lid on top and turn heat to low to keep warm.
Place each meatball onto split buns top with chopped celery blue cheese or ranch dressing.