Rub the base of a 20cm springform cake tin with olive oil and line with greaseproof paper, then rub the paper with oil, too. Melt 50g of chocolate in a heatproof bowl over a pan of gently simmering water, then remove. Snap the Hobnobs into a food processor and blitz with 2 tablespoons of extra virgin olive oil until well combined. Drizzle in the melted chocolate, then pulse again. Pat into the cake tin in a 1cm-thick layer.
Peel the bananas, tear into the food processor, add the cream cheese and dulce de leche, blitz well until nice and smooth, then pour over the biscuit base. Freeze overnight or until needed, transferring to the fridge for 2 hours before serving, or until it’s the slicing consistency you like.
Loosen the edges of the cheesecake with a palette knife, then release from the tin. Shave or grate over the remaining chocolate, and serve. Delicious.