This may just be my favourite thing of all about Christmas – cold, sweet, rich butter slipping down the side of a steaming Christmas pudding. Don't use caster sugar; it will give the butter a grainy consistency.
200g/7oz unsalted butter, softened
400g/13oz icing sugar
3 tbsp Armagnac
Place the butter and icing sugar in a food processor and blitz until smooth. It should have a luxurious consistency and drop easily from a spoon. Stir in the brandy. Place in a bowl and chill in the fridge until ready to serve.