1. Preheat your oven to 375 F (190 C). Line a 12-cup muffin tin with paper liners or lightly grease each cup with non-stick spray.

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

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

4. Pour the wet ingredient mixture into the dry ingredient mixture. Stir gently with a spatula or wooden spoon until just combined. Be careful not to overmix; a few lumps are perfectly fine and will lead to tender muffins. Overmixing can result in tough muffins.

5. Gently fold in the shredded cheddar cheese and chopped fresh chives (if using). Distribute them evenly throughout the batter without overworking it.

6. Divide the batter evenly among the 12 prepared muffin cups. Each cup should be about two-thirds full.

7. Bake for 18-22 minutes, or until the tops are golden brown and a wooden skewer or toothpick inserted into the center of a muffin comes out clean.

8. Let the muffins cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely. They are best enjoyed warm.