Sift the flour into a bowl and mix with baking powder, baking soda, cinnamon and cocoa powder. In another bowl, crack open the egg and whisk gently. Then add sugar, oil and buttermilk to the egg and mix. Peel, mash and fold in the bananas. Finally add the flour mixture and carefully fold in. Put 12 muffin paper cases into the tray and fill in the batter.
Bake in a hot oven for approx. 20-25 minutes until golden. Let rest in the tray for 5 minutes, then decorate with couverture after cooling.