The night before you plan to make the dressing bake cornbread. Preheat oven to 425℉. Spoon shortening into 9 x 13-inch ovenproof pans. Place in oven to heat for about 5 minutes.
Whisk eggs in medium bowl. Stir in the cornmeal mix, milk and oil just until moistened. Carefully tilt to coat the bottom of baking pan with melted shortening. Pour batter into pan.
Bake 25-30 minutes or until toothpick inserted in center comes out clean. Cool then cover or store in a tiptop bag overnight.
Place diced onion and celery in crockpot and add 32-ounces chicken broth. Cover and cook on LOW overnight.
The dressing only needs 4 hours to cook so if you need it later in the day, turn the crockpot off and allow the onion/celery mixture to cool in crockpot until ready to mix all of the ingredients together.
When ready to prepare the dressing crumble the cornbread into the crockpot with the onion/celery mixture. Tear the bread into small pieces and add to the mixture. Add the additional chicken broth, soup, beaten eggs, melted butter, salt and pepper and poultry seasoning. Mix well. Add a few pats of butter to the top of mixture.
Cover and cook on HIGH for 2 hours or LOW for 4 hours.