Superfine sugar

Superfine sugar (caster sugar in the UK) is white sugar ground into crystals smaller than ordinary granulated sugar but not as fine as a powder. Because the crystals are small, they dissolve quickly in egg whites, cream and cold drinks, and they blend smoothly into butter. It is used in meringues, sponge cakes, shortbread, custards and cocktails.

How to do it

To make your own:

1. Put granulated sugar in a food processor or a clean spice grinder.
2. Pulse for 30 to 60 seconds, until the crystals look fine and sandy.
3. Let the dust settle for a minute before you open the lid.

Do not keep going, or it turns into a powder close to powdered sugar, which behaves differently.

Why it works

Fine crystals cut more, smaller air pockets into butter when you cream it, which gives a lighter cake. In a meringue, they dissolve in the egg white before it reaches stiff peaks. Undissolved sugar leaks out as sticky beads of syrup after baking.

How to use it

The same sugar is sold under several names:

• Caster sugar, sometimes spelled castor sugar, in the UK, Ireland, Australia and New Zealand. The name comes from the caster, a small pot with holes in the lid used to sprinkle sugar.
• Superfine sugar in the US, and also baker's sugar.
• Bar sugar in the US, for cocktails, because it dissolves in cold drinks.
• Golden caster sugar, in the UK, is a less refined version with a pale golden color and a light caramel note.

British cake recipes use superfine sugar wherever an American recipe would use regular granulated sugar. In most cases granulated sugar works fine as a swap.

Substitutes

Granulated sugar is the easiest swap, one for one by weight. It is fine in most cakes and cookies. For meringues and pavlovas, grind it first, or add it very slowly while whisking.

Common mistakes

• Swapping powdered sugar for superfine sugar. Powdered sugar is much finer and often contains starch, which changes the texture.
• Measuring it by volume as if it were granulated. A cup of superfine sugar weighs a little more, about 220 g instead of 200 g. Weigh it.

In recipes

You will see "150 g caster sugar", "¾ cup superfine sugar" and "golden caster sugar". To test a meringue, rub a little between your fingers. If it feels gritty, keep whisking.