Where would donuts be without confectioners' sugar? Also known as powdered sugar, the ingredient forms the base of countless enticing glazes, and on its own is an essential topping for countless donuts around the world.
Professional grades of powdered sugar, made by grinding granulated sugar, which is then sorted according to the size of the ground sugar particles, range from 2x, the coarsest, to superfine 14x. The most widely available grade, 10x, is the best for donut glazes—the sugar is fine enough to dissolve completely and quickly in liquid, yielding flawless glazes that dry fast.
Most powdered sugars include a small amount of starch (usually cornstarch), which acts as a stabilizer and anticaking agent. This helps the sugar stay clump-free—especially useful for achieving even sprinkling on powdered donuts.
While confectioners' sugar is widely available in supermarkets, you can also make it at home: Combine one-half cup granulated sugar and three-quarters teaspoon cornstarch in a spice or coffee grinder. Blend on high speed for about one minute until the mixture is ground to a very fine powder. Sift through a fine-mesh strainer and store in an airtight container. Makes three-quarters cup.