Preheat oven to 180 degrees Celsius
Line a muffin pan with cupcake liners
Place the bananas in a large bowl and smash them with a fork
Mix in the egg, butter, oil, sugar, cinnamon and vanilla essence
Mix in the flour, baking powder, bicarbonate of soda together with the cocoa powder and chocolate. Mix until just combined. Do not over mix
Divide the batter equally between the 12 cupcake liners. Should be just over half full
Bake in the oven for 20 minutes or until a toothpick inserted in the center comes out clean
Place on a cooling rack to cool. Store in an airtight container, in the refrigerator for up to 5 days