Preheat oven to 375° and coat your baking dish with cooking spray.
Crumble up the cooked cornbread and add to a large bowl.
Add in the cream of chicken, cream of celery, diced onions, diced celery, stuffing mix, poultry seasoning and chicken broth. Mix until fully combined.
Transfer the dressing to your baking dish. Place the cubed butter on top and bake for 40 - 60 minutes or until browned. Allow the dressing to sit for at least 20 minutes. Over time dressing will stiffen up.