01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners or grease lightly.
02 - In a large bowl, whisk mashed bananas, eggs, vegetable oil, granulated sugar, brown sugar, and vanilla extract until smooth.
03 - In a separate bowl, sift together flour, cocoa powder, baking soda, baking powder, and salt.
04 - Gently fold the dry ingredients into the wet mixture using a spatula until just incorporated; avoid overmixing.
05 - Fold in most of the chocolate chips, reserving a few to sprinkle on top.
06 - Distribute batter evenly among muffin cups, filling each approximately three-quarters full. Top with reserved chocolate chips.
07 - Bake for 18 to 22 minutes until a toothpick inserted into the center emerges with a few moist crumbs.
08 - Allow muffins to cool in the tin for 5 minutes, then transfer to a wire rack and cool completely.