Mix flour, cornmeal, sugar, salt, garlic powder, and baking powder together in a medium-sized mixing bowl.
Add the melted butter, oil, egg, and milk to the dry ingredients. Whisk until everything is combined.Fold in the cheddar cheese and diced jalapeños.
Add the remaining 2 Tablespoons of butter to an 8x8 inch pan or 10-inch oven-safe skillet. Place into the oven for 5 minutes or until the butter melts.
Remove the pan from the oven and immediately pour the batter into the hot pan. This is what helps develop the crispy, buttery crust.
Return to the oven to bake for 25-30 minutes or until golden brown, and a tester comes out clean when inserted in the center.