Set oven to 450 degrees. Pour oil into a heavy skillet and put that in the oven.
Mix cornmeal, flour, baking powder, baking soda, sugar and salt in a bowl.
Add egg to the mixture and enough buttermilk until the batter is thinner than pancake batter.
VERY carefully take the skillet out of the oven and pour oil into batter.
Mix the batter and pour it into the hot skillet.
Return to the oven and bake. Watch carefully after 10 minutes, until brown.
Serve with butter.
