It’s not an ingredient that you’ll see called for too often in American cookbooks, but you’re sure to see custard powder mentioned in cookbooks published in the UK or Australia, or even in the pages of foodie magazines imported from either country. I used some recently in my recipe for Vanilla Slices. Custard powder is not dried, powdered custard. It is actually a powdered mix used to make custard, and it is very similar to the type of mix used to make instant pudding in the US. Just combine it with milk, cook to thicken, and you have custard (or pudding)!
Custard powder is primarily made up of thickeners that give the pudding its texture. Cornstarch is usally the biggest component, since it is great for thickening liquids, disolves easily and is almost foolproof. The powder also contains flavorings – vanilla is the one you’re most likely to find in a “standard” custard powder – and a hint of yellow coloring. Yellow coloring gives the custard just enough color to look as though there are plenty of eggs in it, as most basic custards are thickend with eggs instead of powder.
You can find custard powder at some specialty markets and some markets that specialize in imports from other countries. If you’re traveling abroad, you should be able to find it pretty easily. Birds’s is a big name in custard powder, but even Pillsbury produces it for other markets. If you can’t find it, instant pudding mix is a great substitute.