Preheat the oven to 350ºF. Line a 12 cup muffin pan with paper liners or coat with cooking spray.
In a large bowl whisk together banana, applesauce, canola oil, and egg.
In a medium bowl, whisk together flour, sugar, baking soda, baking powder, cocoa powder, and salt. Add the flour mixture to the banana mixture and stir just until all the flour is incorporated. Fold in the chocolate chips and walnuts.
Divide batter evenly amongst prepared muffin cups. Bake 25 minutes or until a toothpick inserted into the center of one of the muffins comes out clean.