Preheat the oven to 375 degrees F and position a rack in the center. Line a muffin tin with baking cups and set it aside.
In a large bowl mash the bananas with a fork or potato masher then mix in the sugar, egg and applesauce. Sift the flour, cocoa powder, salt, baking soda and baking powder over the banana mixture. Mix lightly with a rubber spatula to combine. Fold in chocolate chips. The batter should be just moistened but still a little clumpy. Don't overmix!
Using a spring-loaded ice cream scoop or spoons, divide the batter between the prepared muffin cups and bake them for about 20 minutes until a toothpick inserted into the middle comes out clean. Transfer them to a rack to cool. Store muffins in an airtight container at room temperature for up to 3 days.