1. Line a 1.2L pudding tin or bowl with a double layer of cling film, leaving plenty overhanging.
2. Put the biscuits in a food processor and blitz until you get a fine crumb. Add the melted butter and caramel and mix well. Use the back of a spoon to spread the mix evenly over the base and up the sides of the pudding bowl. Freeze for one hour.
3. Take the chocolate ice cream out of the freezer and let it soften at room temperature for about 15 minutes. Take the pudding bowl out of the freezer and spoon the ice cream into the biscuit-lined bowl (you want to fill ¾ of the bowl leaving ¼ of space for the Christmas cake layer). Return to the freezer for 30 minutes.
4. Crumble the Christmas cake into small bite size pieces using your hands. Take the pudding bowl out of the freezer and press the cake into the bowl, filling it up as much as possible. Return to the freezer for at least 6 hours, overnight if you can (this will keep for up to a week, so great if you want to prepare in advance).
5. Next, make a chocolate ganache to coat the pudding with and stick on the Maltesers. In a stainless steel bowl break up the chocolate and stand to the side. In a pan, heat the cream until steaming but not boiling. Pour the cream over the chocolate, allow to stand for 2 minutes then stir with a wooden spoon forming a ganache. Allow to cool to room temperature.
6. Take the pudding out of the freezer, tip it out onto a plate and remove the cling film. Spread half of the ganache over the pudding and as quickly as you can stick the Maltesers on. Add more ganache as you go as it will dry. Start from the bottom and work your way up.
7. Once covered in Maltesers return to the freezer for at least another 4 hours. Remove from the freezer 5-10 minutes before serving.
8. To serve, top with a holly decoration and a light dusting of icing sugar.