1. Prepare Your Muffin Tin: Preheat your oven to 375 F (190 C). Line a 12-cup muffin tin with paper liners or grease it thoroughly with butter or non-stick spray. This ensures your muffins won’t stick and makes for easy cleanup.

2. Combine Dry Ingredients: In a large mixing bowl, whisk together the all-purpose flour, unsweetened cocoa powder, granulated sugar, brown sugar, baking soda, and salt. Make sure there are no lumps, especially in the brown sugar, to ensure even distribution.

3. Mix Wet Ingredients: In a separate medium bowl, whisk together the sourdough discard, milk, melted butter, egg, and vanilla extract until well combined and smooth. The melted butter should be cooled slightly so it doesn’t scramble the egg.

4. Combine Wet and Dry Mixtures: Pour the wet ingredients into the dry ingredients. 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 a more tender muffin. Overmixing can result in tough muffins.

5. Fold in Chocolate Chips: Gently fold in the chocolate chips until they are evenly distributed throughout the batter. Again, avoid overmixing.

6. Fill Muffin Liners: Divide the batter evenly among the 12 prepared muffin cups. You can use an ice cream scoop for easy and consistent portioning. Fill each liner about two-thirds full.

7. Bake Until Done: Place the muffin tin in the preheated oven and bake for 18-22 minutes, or until a wooden skewer or toothpick inserted into the center of a muffin comes out with moist crumbs, but not wet batter. The tops should be set and spring back lightly when touched.

8. Cool and Serve: Remove the muffins from the oven and let them cool in the muffin tin for about 5 minutes before transferring them to a wire rack to cool completely. They are delicious served warm, but also great at room temperature.