To make the base use a food processor to whizz up the biscuits into crumbs, or bash them with a rolling pin in a bowl or freezer bag
Mix the melted butter into the biscuit crumbs, and press the mixture into the bottom of a 23cm springform tin until compact and even. Put it in the fridge for 30 minutes to set, or while you make the filling
For the cheesecake filling use a food mixer with a whisk attachment or an electric hand whisk to mix together the cream cheese, cocoa powder and icing sugar until smooth with no lumps
Add the double cream and whisk until it is very thick and holds it's shape
Gently fold in the mini marshmallows
Smooth the mixture into the tin on top of the biscuit base, then put it in the fridge overnight, or for at least 4 hours, to set
Remove from the tin and put on your serving plate. Smooth the sides with a butter knife to create a neater finish
To decorate, melt the milk chocolate and pipe or drizzle it all over the cheesecake
Then whip up the double cream with the icing sugar and vanilla, and pipe it all around the edges of the cheesecake
Sprinkle more mini marshmallows all over the cheesecake, and either crush up half a flake bar and sprinkle that over, or grate milk chocolate over it
Serve immediately, store any leftovers in the fridge and eat within 2 days