Which spirit is traditionally added to butter and served with Christmas pudding?

Brandy is the spirit that is traditionally added to butter and served with Christmas pudding. Sometimes rum, whiskey, or sherry is added to butter in lieu of the brandy.

Brandy butter is particularly associated with the Christmas and New Year holidays in the United Kingdom. It serves as a seasonal alternative to cream, ice cream or custard that is paired with Christmas puddings and warm mince pies.

Brandy butter is the quickest and easiest accompaniment to pies and puddings. It only needs 3 basic ingredients, unsalted butter, icing sugar, and brandy or cognac. Beat the butter, mix the sugar, and add the brandy to taste and you're done!