Add the cream to a pan and heat it until a rolling boil starts.
Break the chocolate into small pieces and add to the pan (make sure all of the chocolate is covered by the cream). Leave for around five minutes.
Quickly whisk until the melted chocolate and cream are combined, and you have a thick, silky mixture.
Quickly beat the mascarpone, cream cheese and icing sugar in a mixer (or using a whisk), just until everything is well combined.
Pour in the chocolate and cream mixture, and again, mix just until everything is silky and smooth.
Add the cranberry sauce and gently stir it in so that it is fairly evenly distributed. Don't stir too much, otherwise your cheesecake filling will be completely pink.
Pour over the base / crust and smooth it out. Cover with clingfilm and place in the fridge overnight.