Prepare "Old Fashion Cornbread" recipe as directed. Cool.
Preheat oven to 350 degrees.
Dice cornbread into 1/2 inch cubes. Do this carefully as cornbread crumbles easily. Discard any small crumbs as they will burn. Toss the cubes in 1 tablespoon of the olive oil and spread into one even layer on a cookie sheet. Bake for 10 to 20 minutes, turning every 5 minutes, until dry and toasted. Cool.
In a cast iron fry pan, heat the remaining oil on medium heat. Saute celery, onion, and pepper until soft and onion is translucent. Add salt and sage, mix to combine. Toss in toasted cornbread to combine. Gradually add warm stock, about 1/4 cup at a time until absorbed. Mix should be moist, but not soaking wet.
Leave stuffing mix in pan and transfer cast iron pan to the oven. Bake for 20 to 30 minutes until top is crunchy and beginning to brown. Allow to set for 5 minutes before serving.
Notes
This recipe can be made without a cast iron fry pan. Instead, prepare as directed using a regular medium-sized skillet. Once stock has been added, transfer mix to a casserole dish lightly sprayed with nonstick spray. Bake as directed.