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

2. In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, unsweetened cocoa powder, baking soda, and salt.

3. In a separate medium bowl, whisk together the sourdough discard, milk, vegetable oil (or melted butter), large egg, and vanilla extract until smooth.

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.

5. Gently fold in the chocolate chips until they are evenly distributed throughout the batter. Reserve a few for sprinkling on top if you like.

6. Divide the batter evenly among the prepared muffin cups, filling each about two-thirds full. If desired, sprinkle the reserved chocolate chips on top of each muffin.

7. Bake for 18-22 minutes, or until a wooden skewer or toothpick inserted into the center of a muffin comes out clean or with moist crumbs attached. The tops should be set and lightly spring back when gently touched.

8. Let the muffins cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely. Enjoy them warm or at room temperature.