Preheat oven to 400℉. Grease an 8x8-inch baking pan and set aside.
In a large bowl, whisk together the cornmeal, flour, sugar, baking powder and salt.
Add the sourdough discard, milk, vegetable oil, melted butter, and egg and whisk until smooth.
Pour the batter into the prepared pan and bake for 25-28 minutes, or until a toothpick inserted in the center comes out clean. Let cool in the pan for 10 minutes, then transfer to a cooling rack to cool fully. Slice before serving.
Video
Notes
You can also use active sourdough stater in this recipe if you prefer. To do so, replace the sourdough discard with active starter (200g).