Firstly, make your base. Crush your gluten free biscuits and 1 Crunchie bar (you could use more if you like in the base). Either place them in a sandwich bag and hit them with a rolling pin or you can place them in a food processor and blitz, but don't over blitz them into a fine dust!
Melt your butter - I do this in the microwave on a medium power (600W) for around 30 seconds to 1 minute. But if it melts before this time, stop - it's done!
Pour your melted butter into your crushed biscuits and mix together in a bowl.
Press your biscuit mixture into the tin you are going to be making your cheesecake in. Press it down nice and firmly. I use a 20cm loose bottom tin (linked above and below).
Place it in the fridge to chill whilst you make your cheesecake top. (I leave mine in the fridge for at least 30 minutes)
To make your cheesecake filling, mix together your mascarpone (cream cheese), icing sugar and vanilla extract. I use my electric hand mixer to do this on a low/medium setting for only about 10-20 seconds. You could use a stand mixer too.
Add in the double cream and keep mixing until it firms up a little. (I mixed on a medium setting for just under 2 minutes for this - try not to over mix though... don't let it split - it's better to stop early than let it split!) It should end up being a nice, fairly thick mixture you can spoon - NOT a pourable consistency.
Fold in your chopped up pieces of Crunchie, so they are evenly dispersed throughout the mixture.
Spread your mixture on top of the biscuit base and place in the fridge to chill overnight.
Mix up your Crunchie spread in a bowl to loosen it up - this will make it easier to spread. Spread it over the top of the chilled cheesecake. I do this whilst it's still in the tin. Place back in the fridge briefly to let the Crunchie spread chill (if you don't have time it wouldn't matter too much here).
Remove from the tin and decorate however you like. I just break up some extra Crunchie bars and cover the top in a random pattern.
Keep refrigerated until serving, or if you have any leftovers. Enjoy!