Melt the sugar in a small frying pan over a medium heat until caramelised. Add the peanuts, then immediately and carefully tip the brittle onto a piece of non-stick baking parchment and leave to cool.
In a microwaveable bowl, melt the dark chocolate in the microwave for 1 min. Stir it well, then set aside.
Remove the bananas from the freezer and blitz in a food processor until they are the consistency of ice cream. Break the cooled brittle into shards and drizzle each bowl of ice cream with some melted chocolate. Mmm!