Tapioca starch is processed from cassava, a staple root crop of the world's tropical countries. The roots are shredded and cooked, and the starch is extracted and refined from the cooking water. The pure starch, known as tapioca flour, is a powerful thickener but becomes stringy if overcooked or stirred too frequently. To counter that tendency, manufacturers process the starch into small balls, which are par-cooked by steaming. When these balls are added to a pudding or pie filling, they provide both thickening power and balls of sweet, chewy gel as a contrasting texture.

Tapioca flour is very neutral, so it can be used in dishes with delicate flavors. It thickens at a lower temperature than most starches, as little as 126 degrees Fahrenheit, so it's ideal for use with delicate ingredients that won't stand up to boiling. It's also useful as a last-minute fix for a sauce that hasn't thickened properly. Tapioca flour is superior to cornstarch for those who cook and bake ahead because sauces and pie fillings will maintain their texture when frozen and thawed. Cornstarch has an unfortunate tendency to "bleed" moisture when thawed, and its consistency suffers.

Quick-cooking tapioca is a form of tapioca "pearls" that is par-cooked a second time, cooking the starches almost completely. The pearls quickly absorb enough of their cooking liquid to rehydrate, thickening the liquid in the process. Quick tapioca is primarily cooked in sweetened milk to make tapioca pudding, but some recipes also call for it in pie filling. It is an effective thickener, though some object to the chewy pearls in their pie. The tapioca can be powdered in a spice mill or blender to make it more unobtrusive, or tapioca flour can be used instead.

Tapioca pudding requires no eggs for thickening, and if milk is used rather than cream it is low in fat. Standard recipes call for milk or cream, but there is no reason to limit your choices. Make kid-friendly versions with fruit juice or brightly-colored tapioca pearls.For a sophisticated adult dessert, use espresso as your cooking liquid. Vanilla-flavored tapioca pudding pairs well with most fruits, and can be layered in dessert dishes for visual appeal. The extra-large tapioca pearls used in bubble tea are available in Asian groceries, and can be prepared at home for use with any favorite beverage.