Preheat the oven to 190ºC, fan 170ºC, gas mark 5. Peel and slice the bananas and arrange in the base of a 1-litre ovenproof dish.
In a separate bowl, place the flour, chilled butter, drinking chocolate and sugar. Rub the mixture together with your fingertips until the mixture resembles fine breadcrumbs.
Stir in the nuts and then sprinkle the mixture over the bananas. Bake the dish for 15-20 minutes or until piping hot.
Remove from the oven and rest for 5 minutes and then serve for a gooey, fruity dessert.
Cook's tip: Try serving this scrummy pudding with a dollop of crème fraîche or warm custard.