Preheat oven to 425F. Line 12-count muffin pan with cupcake liners or spray with nonstick spray. This recipe usually makes 10 muffins, so you will have 2 empty.
In a medium bowl, mash the bananas with a fork. Make sure that there are no large chunks left. Add the yogurt, applesauce, egg, maple syrup/honey, coconut sugar, and vanilla. Mix until it is completely combined. Set aside.
In a large bowl, combine the flour, cocoa powder, baking powder, baking soda, and salt. Mix until fully combined.
Pour the wet ingredients in the dry ingredients. Gently mix until combined. Be careful not to overmix the batter.
Fold in your desired mix-ins, saving some for the top of your muffins.
Spoon batter into liner. Filling each all the way to the top. Top each with a few chocolate chips or nuts.
Bake the muffins for 5 minutes at 425F. Then reduce oven temperature to 350F and continue to bake for an additional 14-16 minutes or until a toothpick inserted into the center of a muffin comes out clean. *Do not open the oven while the oven is reducing in temperature.
Allow muffins to cool in the muffin pan for 5-10 minutes before transferring to a cooling rack.