Hard sauce is not really a sauce at all, and could really more accurately be termed a spread. It is a rich combination of butter, sugar, and alcohol that traditionally accompanies heavy desserts such as plum pudding. Many people associate the sauce with the holidays in particular, when it is often offered with an assortment of desserts. In some parts of the world, it is known as brandy butter, a reference to the two primary ingredients.
To make hard sauce, butter and sugar are creamed together before a flavoring is added. Rum and brandy are two classic flavorings, although other alcohols or liqueurs could be used as well. Extracts of vanilla, almond, or orange could also be used, for cooks who are trying to avoid the use of alcohol. Some cooks also add accents like lemon or orange zest.
The mixture is chilled so that it is cold before serving. Hard sauce may be offered in a central dish, allowing diners to serve themselves, or it may be individually served on each plate. Some cooks use molds to make fanciful shapes that also look more elegant than simple lumps of butter. Gingerbread, fruitcakes, and other holiday foods all pair well with this spread, which is usually mounded on top of a dessert rather than being spread out like a frosting. It may also be garnished with mint, cloves, or other appropriate ingredients.
Any kind of sugar can be used in hard sauce. Many cooks use confectioner's sugar, since it yields a smooth, creamy texture. Granulated white sugar can also be used, although the final product will be more grainy. Some cooks also use brown sugar to make a darker sauce with a molasses-like flavor. This form is more rich and complex in flavor, as a general rule.
Cooks can make this dessert sauce by creaming 0.5 cup (113 g) of butter before slowly adding 1.5 cups of sugar of choice (about 180 g powdered sugar, 300 g granulated sugar, or 330 g packed brown sugar). The mixture should be blended until it is light and fluffy before 2 tablespoons (29.5 ml) of rum, brandy, or a preferred flavoring are added. Once thoroughly combined, the sauce should be chilled until the cook is ready to serve it. It can keep for several days in the refrigerator and many cooks make it ahead of time so that they don't need to worry about it in the flurry of holiday cooking.