Grease a 20cm springform cake tin and layer with the crumbed biscuit mix
Tap the biscuit mix down with the bottom of a glass to make a base
Put the base in the fridge to chill for 20 minutes
Mix the remaining ingredients together in a stand mixer and pour over the biscuit base
Bake for 20 minutes - not a minute more
When the time is up, transfer immediately to the fridge to set overnight
If you use ordinary pouring cream instead of the double cream, it may make the cheesecake lighter but it will be softer and moister and not set quite in the way it should.
Notes
Don't be tempted to leave the cheesecake for even a second over 20 minutes. It should still be wobbly in the centre when you take it out of the oven. This is the secret to this cheesecake being so luxuriously smooth.