Preheat oven to 180°C
In a bowl add the mashed bananas, eggs, maple syrup and mix well
Add the flour and baking powder to the mixture and mix
Remove about 1 cup of the batter to another bowl and add the cocoa powder and milk, mix well
Alternate the 2 batters into a prepared loaf tin
Top with chopped hazelnuts (optional)
Bake for 45-50 minutes