Beat together eggs, sugar, oil, banana, buttermilk, and vanilla until combined.
Add flour, cocoa, baking powder, baking soda, and salt and mix until just combined. Do not overmix or muffins will be tough. Fold in chocolate chips.
Using cookie scoop, divide batter evenly between 12 muffins and bake for 15-17 minutes or until a toothpick comes out clean. Allow to cool for 5-10 minutes, remove from muffin tin and cool on a rack.
Notes
Muffins will last up to 4 days in an airtight container stored at room temperature. PRO TIP: Keep a piece of bread in the container with the muffins to help absorb some of the moisture!