To reheat the pudding, place an upturned saucer at the bottom of a large pan. Put the pudding basin on the saucer and pour hot water around to come three-quarters of the way up the sides of the pudding bowl. Cover and steam for 1-2 hours. Make sure the water doesn’t all evaporate.
Turn the Christmas pudding out onto a plate. Pour the brandy into a ladle and carefully warm over a low heat for 1 minute or so. Light the brandy using a long match and tip over the pudding just before serving with brandy butter.