Use granulated sugar
Grind the sugar in a blender, food processor, or spice grinder
Blend until it becomes a fine powder
Sift the powdered sugar to remove any coarse grains
Regrind any remaining coarse sugar
Use immediately or store in an airtight container
If needed, add a small amount of arrowroot powder instead of cornstarch
If needed, add a small amount of tapioca starch instead of cornstarch
If needed, add a small amount of potato starch instead of cornstarch