Preheat the oven to 200C/180C Fan/Gas 6. Line an 8" square baking tin.
In a large bowl, mash the bananas. Then add the butter, both sugars, vanilla and egg (ensure the butter has cooled a little so the egg doesn’t cook). Mix with a wooden spoon until combined.
Add the dry ingredients: flour, baking powder, baking soda, cinnamon, chocolate and pecan nuts. Stir until just combined.
Pour the batter into the prepared tin and bake for 30-35 minutes; until golden brown and a skewer inserted comes out clean.