Powdered sugar is also known as confectioner's sugar. It is made from granulated sugar that has been ground to a fine powder. Powdered sugar can be made at home by adding one cup of granulated sugar and one tbsp. of cornstarch to a blender and processing at a high speed for several minutes. Powdered sugar is most commonly used in making uncooked frosting or for dusting pastries. Although it is made from granulated sugar, it can not be used as a substitute for granulated sugar when baking. Like flour, powdered sugar is never measured by scooping up with a measuring cup.
Scoop powdered sugar into the top of a sifter and hold over a mixing bowl.
Turn the handle of the sifter to sift the powdered sugar. "The Fannie Farmer Baking Book" recommends sifting confectioner's sugar to remove lumps prior to measuring.
Spoon the sifted powdered sugar into a measuring cup that is either an exact eight ounces or a fraction thereof, depending on how much you need to measure out. For example, if you need to measure ¼ cup, use a ¼ measuring cup instead of an eight ounce glass measuring cup with measurement markers.
Heap the powdered sugar into the measuring cup, without compressing the sugar.
Level off the top of the measuring cup using the back of a knife. Hold the measuring cup over a bowl while eliminating the excess powdered sugar.