Combine cornmeal, baking powder, baking soda, and salt in a large bowl; add 2 eggs, buttermilk, and melted bacon drippings, stir well.
Place a well greased 10-inch cast iron skillet in a 450°F oven for 4 minutes or until hot. Remove skillet from oven, spoon batter into skillet. Bake at 450F for 35 minutes or until cornbread is lightly browned. Cool; crumble cornbread into a large bowl.
Sauté celery and onion in butter until tender. Add sautéed vegetables and remaining ingredients to crumbled cornbread, stirring well. Spoon dressing into a lightly greased 13x9 inch pan. Bake at 350°F for 25-30 minutes.