First of all, preheat the oven to 350°F. Line muffin tins with liners or spray muffin tins with cooking spray. To make your own jumbo muffin liners, see the instructions above in the blog post.
In a stand mixer with the paddle attachment or in a mixing bowl, add bananas and mash.
Next, add the oil and eggs. Beat well until combined. Then, add brown sugar, vanilla, and yogurt.
In a separate bowl, combine flour, cocoa powder, baking powder, baking soda, and salt. Mix with a spoon until combined.
Add the flour mixture to the banana mixture. Mix on low speed with a mixer, just until combined. Add chocolate chips and fold in with a spoon or spatula.
Fill the muffin liners with batter until they are about ⅔ full. Add a few chocolate chips on top of the muffin batter before placing them in the oven if you like.
Bake in the preheated oven for about 15-20 minutes, or until a toothpick inserted in the center of the muffin comes out clean. Do not overbake.
Remove muffins carefully from the muffin pan and place them on a wire rack to cool.