Finely chop / crumble the biscuits. Finely chop the two types of chocolate. Heat the cream with the butter until the butter has melted. Remove the saucepan from the plate, add the chocolate and stir until everything is dissolved. Then add the fine biscuit crumbs and stir in well. Fill into sterilized twist-off jars.
Best kept in the refrigerator. Shelf life approx. 2 weeks.