“Hard sauce” is a mixture of butter, either granulated or confectioner’s sugar, and a flavoring such as rum, brandy, or vanilla. It is not cooked but chilled before use, which gives it a fairly solid texture. This sauce is commonly served alongside fruit cake or plum pudding.
A sauce served with Christmas and other rich puddings, which is made with butter and either superfine or brown sugar. It is usually flavored with brandy or rum and is called hard sauce because it becomes firm when cold. Some variations may include ground almonds or stiffly beaten egg white. The sauce is often sprinkled with grated nutmeg before serving.