Heat the oven to 180C, 160C fan oven, gas mark 4.
Stir the melted butter into the crushed biscuits and spread over the base and up the sides of a shallow, 20cm loose-based, fluted flan tin, pressing with the back of a spoon to firm.
Bake for 7-10 minutes until golden then leave to cool.
Slowly melt the butter and sugar together in a small, non-stick saucepan and stir with a wooden spoon to dissolve the sugar.
Stir in 200g of the caramel and bring to the boil, stirring all the time, until very smooth.
Pour into the cold biscuit base and leave to cool and set.
When the caramel is cold, whip the cream until it just begins to hold its shape. Fold in the coffee and continue whisking until the cream is lightly whipped.
Slice the bananas into a bowl and stir in the lemon juice. Spoon the bananas on top of the caramel followed by the whipped cream. Sprinkle over the chocolate and any remaining caramel in the jar just before serving.
The pie will keep chilled for several hours before serving.
For a gluten-free version, use gluten-free shortbread to replace the sweet-meal biscuits.