Preheat oven to 425° and place a 10 inch cast iron skillet in the oven as it preheats.

In a large mixing bowl, add cornmeal, all purpose flour, baking powder and kosher salt and stir to combine. Add milk, vegetable oil and an egg, mixing well. 

Using pot holders, remove the skillet from the oven when it has preheated. Melt 1 tablespoon butter in bottom of skillet.

Pour batter into skillet and spread evenly. Bake for 20 minutes or until a toothpick inserted in center comes out clean. Remove from oven to cool completely. 

Lower oven temperature to 375°.

Lightly toast 4 slices of bread and cut into 1 inch pieces. Set aside. 

Place a large skillet over medium- low heat. Add butter with diced onion, celery and garlic. Cook over until vegetables are softened, about 15 minutes. Stir in heavy cream, stirring just until cream starts to bubble. Remove from heat and set aside.

In a large bowl, crumble cornbread completely. Add toast and vegetable and cream mixture. 

In another bowl, whisk together 2 cups of chicken broth and eggs. Stir into cornbread mixture. Add an additional 1/2 cup of chicken broth if the mixture is dry. Stir in sage, salt and pepper.

Spray a 4 quart casserole dish or 9 x 13 baking pan with non stick cooking spray. Fill with dressing mixture and spread evenly. 

Cover with foil and bake for one hour. Remove cover and bake an additional 30 minutes or until top is browned and dressing is cooked through. 

Serve immediately.