Heat the oven to 200C/180C fan/gas 6. Blitz 50g of the hazelnuts in a small food processor until they resemble fine breadcrumbs, then tip into a bowl with the chocolate.

Roll the pastry out to a round roughly 30cm in diameter on a sheet of baking parchment. Scatter the chocolate and hazelnut mixture over the pastry circle, leaving a 5cm border. Top with the bananas and most of the remaining hazelnuts, then fold the edges of the pastry over. Transfer the galette to a baking sheet along with the baking parchment, then chill in the fridge for at least 10 mins.

Remove from the fridge and sprinkle the sugar over the galette, then bake for 25-30 mins, or until golden and puffed up. Scatter over the remaining hazelnuts and serve with a scoop of vanilla ice cream, if you like.