Put the skillet in the oven and preheat to 375 degrees.
Combine the dry ingredients except for the baking soda in a bowl.
In another bowl, mix the buttermilk and the baking soda.
In a small bowl, beat the egg with the sugar until combined.
Add the oil and mix until combined.
Pour this mixture into the buttermilk/baking soda and mix.
Once preheated, toss the butter into the skillet and let it melt.
Meanwhile, pour the wet ingredients into the dry, and mix in as few strokes as required to make the dough come together.
Pull the skillet out of the oven, swirling to get the butter covering the bottom and sides of the skillet.
Pour the batter immediately into the pan, smoothing the top, then back into the oven for about 25 minutes, or until golden brown and pulled away from the sides of the pan (Perform toothpick test if required).
Turn out onto a cutting board, cut into wedges, and serve.