1. Preheat oven to 350°F (175°C) and line a 12-cup muffin tin with liners or grease with coconut oil.

2. Whisk flour, cocoa powder, baking soda, baking powder, and sea salt together in a large bowl until evenly combined.

3. In a separate bowl mash bananas then whisk in sourdough starter, maple syrup or coconut sugar, melted coconut oil, eggs or flax eggs, and vanilla extract until smooth.

4. Pour wet ingredients into dry ingredients and gently fold with a spatula until no streaks of flour remain, taking care not to overmix.

5. Toss chocolate chips in a small amount of flour mixture, then fold into the batter along with nuts or seeds if using.

6. Let batter rest at room temperature for 20–30 minutes to allow sourdough to ferment and develop flavor, if desired.

7. Spoon batter into prepared muffin cups, filling each about three quarters full.

8. Bake for 18–22 minutes or until a toothpick inserted into the center comes out with moist crumbs and muffin tops are springy.

9. Cool muffins in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.