Chop the cake coarsely, divide between 4 small ovenproof dishes (such as ramekins), pour the brandy over them equally, and let sit for 20 minutes.
While it is sitting, mix together the cheese, the white sugar, the yoghurt and the vanilla.
After 20 minutes, spoon the mixture over top the Christmas cake pieces, then refrigerate for at least 1 1/2 hours - you want it to set firmly.
Heat your broiler (aka grill in the UK) and get it hot. Sprinkle the brown sugar over top the creams. Put the creams under the broiler, and let the sugar burn until it melts and turns a caramel colour.
Remove from the heat, let cool a bit, then serve either right away, chilled or room temperature -- whatever you feel like.
Ratio is 2 mascarpone cheese to 1 cake.Click on mascarpone cheese ingredient line to see substitutes for use in North America. You can replace the brandy with orange juice.If you have a cooking blow torch, you can use that to melt the sugar instead of firing up your broiler or grill.