I found the recipe for this cake online, but I've made a few changes so here's my English version. I hope you enjoy it!
160g plain flour (I prefer to use brown)
1 teaspoon baking powder
150g salted butter
100g dark chocolate
Start by melting 30g of the butter in a frying pan and fry the sliced bananas until they have started to brown. Add a tablespoon of the sugar and continue to cook until it is nicely caramelised. Remove the pan from the heat and leave it to cool.
Heat the oven to 180°
Place the eggs and the rest of the sugar in a mixing bowl. Mix them using an electric whisk until the mixture is pale yellow and doubled in volume. Fold in the flour, sifted with the baking powder. Melt the rest of the butter and fold it in to the mixture. Now add the caramelised bananas (and the accompanying caramel) and chopped chocolate. Pour the mixture into a loaf tin that you have greased and floured, and cook for 45 minutes.
Even though it may be difficult to wait (it smells so good when it comes out of the oven!), leave to cool fully before serving. The chocolate will remain nice and melted for quite a while. If you don't eat it all immediately, keep it in an airtight tin, it tastes just as good, if not better, the next day.