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

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

3. In a separate medium bowl, whisk together the sourdough discard, milk, melted butter, egg, and vanilla extract until well combined and smooth.

4. Pour the wet ingredients into the bowl with the dry ingredients. Stir gently with a spatula or wooden spoon until just combined. Do not overmix; a few lumps are fine.

5. Gently fold in the chocolate chips until they are evenly distributed throughout the batter. Avoid overmixing.

6. Divide the batter evenly among the 12 prepared muffin cups, filling each cup about two-thirds full.

7. Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the tops are golden brown and a toothpick inserted into the center of a muffin comes out clean. The muffins should feel springy to the touch.

8. Remove the muffins from the oven and let them cool in the muffin tin for a few minutes before transferring them to a wire rack to cool completely.