Preheat the oven to 180 ° C. Grease a 24 cm x 13 cm loaf pan.
Mix the butter and sugar together. Gradually add the eggs, vanilla essence and the bananas. Alternately stir in flour, mixed with the baking powder, and buttermilk. Finally fold in the chocolate. Pour the dough into the loaf pan and bake for about 80 minutes. Do a chopstick test after about 70 minutes. Then take the cake out and let it cool down in the tin for about 10 minutes before removing it.
Tip: It is important that the bananas are very well ripened. The cake will keep in an airtight container for up to 3 days.