Preheat the oven to 350℉. Line a 9x5-inch loaf pan with parchment paper and spray with cooking spray. Set aside.
In a small bowl, mix together the flour, baking soda and salt. Set aside.
In a large bowl, combine the mashed bananas, sourdough discard, brown sugar, granulated sugar, and egg. Whisk to combine. Add the melted butter and mix until smooth.
Add the flour mixture to the bowl of wet ingredients and mix until just combined and no dry spots remain. If adding chocolate chips (optional), fold them in until evenly distributed.
Pour the batter into the prepared baking pan. Bake for 60-65 minutes, or until a toothpick inserted in the center comes out clean. Remove from the oven and let cool in the pan for 10 minutes. Remove the loaf from the pan (you can lift it up with the parchment paper), and transfer to a cooling rack to cool fully before slicing and serving.
Video
Notes
Nutrition information is for a banana bread without chocolate chips, and given per slice (10 slices per loaf). To use active sourdough starter, replace the sourdough discard with active starter (200g). Continue with the recipe as written. To add walnuts (or other nuts), add ½ cup coarsely chopped nuts after you mix in the dry ingredients.