In a large pot on medium heat, add 8 cups of water, chicken breasts, celery, onion, poultry seasoning, and minced garlic. Boil for 40 minutes.
In a medium bowl, add chicken breasts, and shred into large pieces.
Reserve the chicken stock to use later in the assembly.
Cornbread
Preheat oven to 425°F.
Add vegetable oil to a cast iron skillet and add to oven. Cook for 3 minutes.
In a bowl combine dry ingredients (corn meal and sugar).
Mix in buttermilk and eggs. Remove skillet from the oven and pour vegetable oil to the cornbread mixture. Mix well.
Pour mixture into the skillet, place in the center of the oven, and bake for 20-25 minutes.
Remove cornbread from the oven.
Assembly
Preheat oven to 350°F.
In a large bowl add cornbread and break up into large pieces.
Mix into the cornbread, butter, cream of celery and cream of chicken with herbs, diced bell pepper, onions, celery, and sage.
Add shredded chicken breasts and pour in 5 cups of chicken stock. Mix well into a thick by "creamy" consistency. If it's not loose enough, add 1 more cups of stock. This will keep it from being dry while baking. Taste and see if more seasonings are needed. Add 1 tsp of chicken bouillon if necessary.
Pour cornbread mixture into a casserole dish. Cover with aluminum foil.
Bake at 350°F for one hour.
Notes
If you don't have cream of chicken or cream of celery, add 1 cup of milk and 1/2 cup of heaving whipping cream.