Make Cornbread: The night before, make the cornbread. Preheat oven to 425 degrees F.
Thinly coat the bottom of a standard Pyrex pie plate, or 9-inch square baking pan, with vegetable oil. Put pan in oven while it is preheating and you are mixing the cornbread batter.
In a mixing bowl, blend together the cornmeal, flour, salt and baking powder. Stir in the egg and about 3 T vegetable oil. Add milk and mix thoroughly by hand. The consistency should be a thick, but not "doughy, " liquid. It may be necessary to add a little more milk. Pour into preheated pan and bake for 30 minutes or until slightly brown on top.
Let cool in pan for 30 minutes. Remove from pan and break up into very large chunks in a large mixing bowl. Let stand overnight, uncovered. This will ensure that it is dry and stale.
Make Turkey Broth: The night before, make the turkey broth. Bring about 12 C of water to a boil in a large pot. Thoroughly rinse turkey neck, giblets and gizzard. Add turkey parts, onion, celery leaves and celery stalk to water, cover and reduce heat to a low simmer. Simmer on very low heat for 2 hours. Strain the broth, cover, cool quickly and refrigerate.