Place the biscuits into a food processor and pulse until the mixture resembles fine breadcrumbs. Transfer to a mixing bowl and stir in the melted butter, mixing well to combine.
Place the mixture into a lightly greased 20cm/8in loose-bottomed cake tin and press down into the base and up along the sides. Place in the fridge to chill for 30 minutes.
Spoon the dulce de leche over the biscuit base, and then cover with a layer of sliced bananas. Spoon the whipped cream on top and decorate with grated chocolate.
Slice into wedges and serve.