Preheat the oven to 170° C w/ fan.
Line the loaf tin w/ baking parchment (all sides - crosswise).
Mix flour, baking powder & cocoa; set aside.
Peel the bananas & mash the bananas like you mash cooked potatoes; finally use a fork. Some small bits should remain. Set aside.
Mix butter, sugar, vanilla sugar & salt with a handheld electric mixer.
Add eggs & mix well.
Add flour mix & mix until you get a soft dough.
Add the banana mess & fold in w/ a spoon.
Fill the mess in the loaf pan.
Peel the last banana & slice into 2 halves. Add the halves on top of the mess.
Bake in the oven for about 50 min.
Make the famous test w/ the wooden pin...
Let it cool down for 10-15 min; then get the banana bread out fo the loaf tin & let it cool down.