It's best to serve Christmas English pudding warm! You can warm individual slices in the microwave before serving, or steam the whole cake for a couple minutes until warm if you've made it ahead of time and have stored it in the fridge or your pantry. You can enjoy it on its own or with a vegan brandy sauce, vegan ice cream, or vegan whipped cream. It's traditionally served flambéed, which means it's covered in brandy and then lit so a flame forms. I don't recommend this unless you know how to do it without burning your fingers.