Words by Simon Difford
Powdered or superfine sugar is simply granulated or caster sugar than has been ground into a fine powder so that is dissolves easily. It is different to icing sugar as this usually has cornstarch, wheat flour or calcium phosphate added to prevent it from forming clumps. If not using sugar syrup then we recommend using powdered sugar in place of granulated or caster sugar.
To make powdered sugar simply grind normal granulated or caster sugar in a mortar and pestle or a coffee grinder.