Put an 8-inch square pan on a rack in the middle of the oven. Preheat the oven to 400 degrees.
When the oven is hot, combine the dry ingredients in a bowl.
Add milk, oil, and egg. Stir with a fork until dry ingredients are just moistened, scraping the sides of the bowl frequently.
Let the batter rest for 2-3 minutes. Add the butter to the pan in the oven.
When the butter has melted, remove the pan and make sure that the bottom is coated with butter.
Pour the batter into to pan.
Bake for 25-30 minutes, or until a toothpick comes out clean and the top is golden brown.