Add the dark chocolate, cream, and butter to a large glass bowl. Cover and microwave for 1 minute. Let sit for 3 minutes, then stir until smooth and combined.
Roughly crush the biscuits and add them to the bowl along with the pistachios and cranberries. Mix until well combined.
Spoon the mixture onto a large piece of clingfilm. Shape into a log, roll up the clingfilm, and twist the ends to seal. Refrigerate overnight until firm.
Roll the salami in icing sugar to coat. Slice and serve. Keep chilled until ready to use.
