Preheat the oven to 350°F (175°C).
Melt margarine or butter in a pan over medium heat.
Cook chopped celery and onion until soft.
In a big bowl, combine cornbread, celery, and onion.
Pour chicken broth and beaten egg into the mix.
Add seasonings: poultry seasoning, sage, salt, and pepper.
Gently toss to moisten the cornbread evenly.
Use an 8-inch square or 1 1/2-quart casserole dish.
Transfer the mixture, spreading it evenly.
Bake for 40-45 mins until heated and slightly crispy.
Stuff a 12-pound turkey with the dressing for roasting.