Put the bacon drippings in a 9 or 10-inch well-seasoned cast iron skillet and put the skillet into the oven. Then preheat the oven to 400°F with the skillet inside.
Whisk together all the dry ingredients (cornmeal, baking soda, salt, sugar if using) in a large bowl.
In another bowl, beat the egg (if using) and buttermilk until combined, then mix that into the bowl of dry ingredients. Stir in the melted butter.
When the oven is hot, take out the skillet (carefully, as the handle will be hot!). Add the cornbread batter and make sure it is evenly distributed in the skillet.
Bake at 400°F for about 20 minutes, or until the edges are beginning to brown and a toothpick inserted in the center of the bread comes out clean.
Let the bread rest for 10 to 30 minutes in the skillet before cutting it into wedges and serving.
