Use plain chocolate, not milk, as it has a much more intense flavour. When cooking always use chocolate which is labelled as having at least 50% cocoa solids.
If you're not eating the pudding straight away, allow to cool then remove pleated foil and greaseproof paper. Cover tightly with a clean piece of foil and store in a cool place for up to 3 months. To reheat on Christmas day, steam (following the method above) for 1 hour.
Alternatively, you can reheat the pudding in a microwave oven - always follow the microwave manufacturers' instructions with regards to power settings and reheating times - sugary foods such as puddings (and mince pies) attract the microwaves and can get extremely hot so you must always give a 'standing time' to allow the temperatures to even out. Do not add additional alcohol to the pudding before reheating in the microwave.
Finely chopped left over Christmas pudding makes a great ice cream folded into softened vanilla ice cream, even the kids will like it ... ... ... ... ... ... ... ... . I promise.