Castor sugar is a kind of granulated sugar made from sugarcane. It is also known as very fine sugar, superfine sugar, baking sugar, or baker’s sugar. Castor sugar is common in grocery stores in the United Kingdom; in the United States, you’re more likely to find it labeled as superfine sugar.
You can use caster sugar in any recipe that calls for granulated sugar. Because of its small grain size, caster sugar dissolves easily in liquid. Uses for caster sugar include:
1. Pudding: Caster sugar will quickly melt in heat, and you can use it in pudding or custard recipes. You can also use caster sugar to make ice cream and sorbet.
2. Airy desserts: You can use caster sugar to make soufflés, meringues, whipped cream, and mousses, among other light and airy desserts. (Avoid using caster sugar to make icing or frosting because the sugar will not dissolve completely, and the frosting will be gritty—powdered sugar is the go-to sugar for buttercream frosting and icing.)
3. Baked goods: You can substitute caster sugar for granulated sugar at a 1:1 ratio. It dissolves more easily and completely in batter, so bakers prefer it when making delicate sponge cakes. Caster sugar also creates a slight textural difference in baked goods: cookies made from caster sugar are more light and airy.
4. Sweetener: Dissolve caster sugar in beverages as a sweetener. Caster sugar is a popular choice among bartenders when creating simple syrup to make cocktails.