Combine granulated sugar, water and ginger in a small saucepan and warm over low heat, stirring until the sugar is dissolved, until your water just reaches a low simmer. Immediately remove from heat.
Place cranberries in a large bowl, and pour syrup mixture to cover the cranberries. Cover and refrigerate for 8 hours or overnight.
Thoroughly drain cranberries over a bowl. If you wish you can reserve the steeping liquid (it makes a good cocktail syrup).
Place superfine sugar in a shallow bowl, and working in batches, add cranberries. Roll them around the sugar until well coated, then transfer them to a baking sheet to completely dry, at least an hour. Store in an airtight container in a cool place for up to a week.
Notes
Storing any leftovers in an airtight container in your refrigerator for up to a week.Do not boil the sugar water, or the cranberries will pop as you add them.If you do not have superfine baking sugar, you can add granulated sugar to a high speed blender or food processor and pulse till a super fine texture is achieved.