Confectioners' sugar, or icing sugar, is very fine sugar mixed with cornstarch. Ideal for frostings and glazes, icing sugar dissolves quickly and is also good for dusting on top of pastries, brownies and other treats. Called icing sugar in Great Britain, the sugar blend contains only about 3 per cent cornstarch to prevent the finely ground sugar from caking. The blended substitute can be used in any application that calls for conventional confectioners' sugar.
Measure out 1 cup granulated sugar for every 1 cup of icing sugar you need for your recipe. It's a 1-to-1 ratio, so as much icing sugar as your recipe calls for is as much granulated sugar you need.
Measure 1 tablespoon of cornstarch for every 1 full cup of granulated sugar you need. If you only need a 1/2 cup of sugar, use only a 1/2 teaspoon of cornflour.
Place both sugar and cornstarch in the needed amounts in a blender. A food processor will not render the desired effect.
Blend on high for several minutes and then use as needed in your recipe.