In a food processor, blitz the almonds until finely chopped (but not ground). You can do this by hand, but make sure you chop finely. Add the biscuits and give it a few pulses so they crush and mix with the almonds.
Melt the butter and add to the biscuits and combine well. Press the mixture into the tart tin and set aside.
In a saucepan, add sugar and butter and heat until the sugar has dissolved. Add the caramel and stir until combined, then take it off the heat and pour the mixture over the biscuit base. Scatter a small amount of salt flakes across the caramel filling before placing in the fridge for at least an hour (or even over night).
To finish the pie, whip the cream and vanilla until peaks form. Slice the bananas, toss them in a bit of lemon juice to prevent them from going brown too quickly, and arrange the slices on the top of the caramel base. Top with the whipped cream, neatly spread across the cake – and finish with finely chopped dark chocolate.