1. 1. Prepare your oven and muffin tin: Preheat your oven to 375 F (190 C). Line a 12-cup standard muffin tin with paper liners or grease it well with non-stick spray. This prevents sticking and makes for easy cleanup.

2. 2. Combine the dry ingredients: 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. 3. Mix the wet ingredients: In a separate medium bowl, whisk together the sourdough discard, milk, vegetable oil, egg, and vanilla extract until well combined and smooth.

4. 4. Combine wet and dry mixtures: 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 a more tender muffin. Overmixing can result in tough muffins.

5. 5. Fold in the chocolate chips: Gently fold in the chocolate chips until they are evenly distributed throughout the batter.

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

7. 7. Bake until golden: 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 golden brown and spring back when lightly touched.

8. 8. Cool before serving: Let the muffins cool in the muffin tin for 5 minutes before transferring them to a wire rack to cool completely. This helps them set and prevents them from getting soggy.