Line the sides of a 20cm round, spring-form tin with strips of cling film (use some water to help the cling film stick) and line the base with a disc of baking paper.
Place the biscuits in a freezer bag and finely crush with a rolling pin.
Melt the butter in a non-stick saucepan over a low heat, add the biscuits and combine.
Spoon into the base of the tin, pressing down with the back of spoon to level. Chill for 15 minutes.
To make the filling, heat the butter and sugar in the same pan and stir over a low heat until combined. Add the condensed milk and bring to the boil, stirring continuously, for 2-3 minutes or until dark golden, taking care that the mixture doesn’t catch on the bottom. Do not allow to boil for too long or it will become grainy. Add the vanilla extract and pour into the tin.
Pour into the tin on top of the biscuit base. Chill in the fridge for a minimum of 1 hour or up to 24 hours.
Peel and slice the bananas. Once the caramel and biscuit base has been in the fridge for at least an hour, arrange the bananas in neat rounds on top of the caramel.
Whip the cream to soft peaks and spoon over the bananas, then level on top before chilling in the fridge for an hour.