Butter and line a spring-form pan with parchment paper. Put the cookies into a plastic food bag and crush to crumbs using a rolling pin. Transfer the crumbs to a bowl and pour over the melted butter. Mix thoroughly until the crumbs are coated then tip into the tin and press down firmly to create an even layer. Chill in the fridge for 1 hour.
Slice the vanilla pod in half lengthways and scrape out the seeds using the back of a knife. In a bowl mix the shake mix, cream cheese, vanilla pods and double cream and mix with an electric blender until combined well. Spoon the mixture onto the biscuit base and smooth evenly. Leave in the fridge for at least an hour before serving.