Preheat oven to 180 degrees. Line and grease a square brownie pan.
Whisk the mashed banana and cocoa powder till no lumps.
Add the remaining ingredients one after the other except the pecans and fold in till you have a moist and thick batter.
Spread into the prepared pan and top with the pecans.
Bake for 30 minutes or till the top is firm to touch.
Cool completely in pan before pulling out the brownie. Cut and enjoy!