Whisk up the double cream until it is light, fluffy and doubled in size.
Mix in the condensed milk with the cream until the mixture becomes thick.
Chop up the chocolate bars into very small pieces.
Then mix all of this together with the mixture.
Line a baking tray with tin foil. You need to line up all the biscuits very precisely. You must remember where you put them as you will need to line the up exactly the same later.
Pour the mixture onto the aligned biscuits. This is where you have to be very careful. You will have to put another layer of biscuits on top of the mixture. If they are not aligned exactly then it will not work when you cut the sandwiches individually to eat.
Place them flat in a freezer and leave overnight.
Cut into sandwiches when fully frozen, using a knife dipped in hot water for easier cuffing. You do not have to use crunchie bars.
You could use any other chocolate or alternatively you could make it healthier and add fruit instead.