1. Preheat your oven to 400 F (200 C). Line a 12-cup muffin tin with paper liners or grease it thoroughly to prevent sticking.

2. In a large mixing bowl, whisk together the all-purpose flour, yellow cornmeal, granulated sugar, baking powder, baking soda, and salt. Make sure there are no lumps and everything is evenly distributed.

3. In a separate medium bowl, whisk together the sourdough discard, buttermilk, melted butter, and the egg until well combined. The mixture should be smooth and uniform.

4. Pour the wet ingredient mixture into the dry ingredient mixture. Stir gently with a spoon or spatula until just combined. It’s okay if there are a few small lumps; overmixing will lead to tough muffins. The batter should be thick but pourable.

5. Divide the batter evenly among the 12 prepared muffin cups. You can use an ice cream scoop for easy portioning, filling each cup about two-thirds full.

6. Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until the tops are golden brown and a wooden skewer or toothpick inserted into the center of a muffin comes out clean.

7. Once baked, remove the muffins from the oven and let them cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely. They are delicious served warm or at room temperature.