1. 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.

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 medium bowl, whisk together the sourdough discard, milk, melted butter, large egg, and vanilla extract until well combined. The mixture should be smooth and uniform.

4. Pour the wet ingredient mixture into the dry ingredient mixture. Stir gently with a spoon or spatula 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 chocolate chips until they are evenly distributed throughout the batter. Again, avoid overmixing.

6. Divide the batter evenly among the 12 prepared muffin cups. You can use an ice cream scoop or two spoons for this. Fill each cup about two-thirds full.

7. Bake for 20-25 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. Remove the muffin tin from the oven and let the muffins cool in the tin for a few minutes before transferring them to a wire rack to cool completely. Serve warm or at room temperature.