What is Castor Sugar?

Castor sugar is a very finely wrought sugar product. It isn't powdered sugar (sugar to which anti-clumping agents like cornstarch have been added). It's a granulated sugar, but the granules are very tiny. In the U.S., castor sugar is often called superfine sugar. If you aren't a sugar purist (and I'm so not), you can approximate castor (or superfine) sugar by processing regular old granulated sugar in a spice or coffee grinder. Once ground, it'll dissolve fast and uniformly in your cooking projects.

One of my oft repeated suggestions here is for herb folk who like to cook to invest in a coffee grinder dedicated to spice and herb use. It'll make life easier -- and tastier -- in the long run. You can pick one up on sale for under $20, and most have the power and deep well necessary for fast and uniform herb processing.