1. Prepare Your Oven and 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, baking soda, and salt. Make sure there are no lumps and the ingredients are evenly distributed. This step is crucial for an even rise.

3. Mix Wet Ingredients: In a separate medium bowl, combine the sourdough discard, large egg, melted unsalted butter, and vanilla extract. Whisk until everything is well combined and smooth.

4. Add Mashed Bananas: Gently fold the mashed ripe bananas into the wet ingredient mixture. The bananas should be very ripe, with plenty of brown spots on the peel, as this provides the best flavor and natural sweetness.

5. Combine Wet and Dry Mixtures: Pour the wet banana mixture 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 of flour are perfectly fine. Overmixing can lead to tough muffins.

6. Fold in Chocolate Chips: Add the semi-sweet chocolate chips to the batter and fold them in until they are evenly distributed. Again, avoid overmixing.

7. Fill Muffin Cups and Bake: Divide the batter evenly among the 12 prepared muffin cups, filling each about two-thirds full. Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until a wooden skewer or toothpick inserted into the center of a muffin comes out clean.

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.