To make powdered sugar at home, use granulated sugar and optionally cornstarch if you want to prevent clumping. Put the granulated sugar (and cornstarch if using) into a high-powered blender, food processor, or spice/coffee grinder. Blend or pulse until the sugar turns into a fine, fluffy powder, which usually takes from 30 seconds to a few minutes depending on your equipment. One cup of granulated sugar yields about two cups of powdered sugar. If you want to keep it from lumping, add about 1 tablespoon of cornstarch per cup of sugar before blending. Use immediately or store in an airtight container for later use. Sifting before use can help achieve a smooth texture if lumps form.
