Cornstarch by John Spottiswood.

This silky powder is used to thicken sauces, gravies, and puddings. Like other starch thickeners, cornstarch should be mixed into a slurry with an equal amount of cold water before it's added to the hot liquid you're trying to thicken. You then need to simmer the liquid, stirring constantly, for a minute or so until it thickens. Cornstarch doesn't stand up to freezing or prolonged cooking, and it doesn't thicken well when mixed with acidic liquids. Cornstarch is called cornflour or maize cornflour in Britain, Australia, and New Zealand. Don't confuse cornstarch with the finely ground cornmeal that Americans call corn flour.