1. Preheat your oven to 375 F (190 C). Line a 12-cup muffin tin with paper liners or grease it well.

2. In a medium bowl, whisk together the all-purpose flour, baking soda, salt, and ground cinnamon (if using). Set this aside.

3. In a large bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth. Beat in the egg and vanilla extract until well combined.

4. Stir in the mashed bananas and sourdough discard into the wet ingredient mixture until just combined. Do not overmix at this stage.

5. Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix the batter; a few lumps are perfectly fine and help keep the muffins tender. Overmixing can lead to tough muffins.

6. Gently fold in 1 cup of the chocolate chips. Distribute the batter evenly among the 12 muffin cups. Sprinkle a few extra chocolate chips on top of each muffin for a beautiful finish.

7. Bake for 20-25 minutes, or until a wooden skewer inserted into the center of a muffin comes out clean or with moist crumbs attached. The tops should be golden brown.

8. Let the muffins cool in the muffin tin for 5-10 minutes before transferring them to a wire rack to cool completely. This helps them set and prevents them from getting soggy.