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