1. Coat bottom and sides of a 10-inch cast-iron skillet with bacon drippings; heat in a 450° oven for 10 minutes. (Skillet may smoke a bit.)
2. Whisk together buttermilk and egg. Add cornmeal, stirring well.
3. Stir in baking powder, baking soda, and salt. Pour batter into hot skillet.
4. Bake at 450° for 15 minutes. Serve with butter.