Crush biscuits to crumbs, and add to molten butter, mixing well. Spoon into 20cm loose bottomed cake tin, creating a lip at the side to contain the caramel.

Add sugar and butter for the caramel into a non stick pan on a low head. Stir until sugar dissolves. Add condensed milk and bring to the boil for a minute, stirring all the time - it should thicken nicely.
Or you could use 400ml of dulce de leche ready made.
Pour or spoon onto the chilled base and return to the fridge for an hour.

Slice the bananas creating disks about 1/2 cm deep. Layer them on top of the caramel. Whip the cream until firm and spread on top. Grate the chocolate finely and sprinkle on top of the cream.