1. Prepare Your Muffin Tin: Start by preheating 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, granulated sugar, unsweetened cocoa powder, baking soda, and salt. Make sure there are no lumps and the cocoa powder is fully incorporated, creating a uniform brown mixture.

3. Mix Wet Ingredients: In a separate medium bowl, whisk together the sourdough discard, milk, melted butter, large egg, and vanilla extract until well combined and smooth. The mixture should look slightly creamy.

4. Combine Wet and Dry Mixtures: Pour the wet ingredients into the bowl with 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 result in tender muffins. Overmixing can lead to 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 Cups: Divide the batter evenly among the 12 prepared muffin cups. Each cup should be about two-thirds full.

7. Bake the Muffins: 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 clean. The tops should be set and lightly spring back when gently pressed.

8. Cool and Serve: Once baked, remove the muffin tin from the oven and let the muffins cool in the tin for 5 minutes before transferring them to a wire rack to cool completely. Enjoy them warm or at room temperature.