Preheat oven to 400°F (200℃) and line a 12-cup muffin pan with muffin liners. Set aside.
In a small bowl, whisk together flour, cinnamon, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy, 2-3 minutes.
Add the mashed banana, sourdough discard, egg, vegetable oil, and vanilla extract. Mix until combined. Add the dry ingredients to the wet ingredients and mix until just combined and no dry spots remain. If using (optional), fold in chocolate chips or walnuts until combined.
Use a spoon or cookie scoop to fill the lined muffin cups about ⅔ full with batter. Sprinkle each muffin with turbinado sugar.
Bake for 22-24 minutes until golden brown and a toothpick inserted in the center comes out clean. Let cool for 10 minutes in the pan, then serve or transfer to a cooling rack to cool fully.
Video
Notes
1 serving = 1 muffin. Nutrition information is calculated without the chocolate chips or walnut add-ins. To make this recipe with active sourdough starter, replace the sourdough discard with active starter (200g). You do not need to change any other ingredients in the recipe. I am in the process of shooting new images for this recipe! The ingredients and recipe listed above are correct, but the images / video are from an older version of the recipe. Hang tight, and this will be updated soon!