The best way to thicken tapioca is with more tapioca. The main ingredient in the bumpy little cream pudding most are familiar with is a thickening agent useful in fruit pies, sauces and even meat gravies. The pearl tapioca from the pudding is one form of a starchy flour derived from the root of the cassava plant. In its smoother form, tapioca may be called tapioca flour, starch or cassava flour. Whatever name you find it under, it is a thickening agent that has several advantages over cornstarch or wheat flour in some applications.
Add pearl tapioca to an overly thin tapioca pudding mixture. Make sure to be consistent in the use of instant or regular pearl tapioca. Most instant puddings, including tapioca, are mixed cold, while regular pearl tapioca must be stirred and heated, then cooled to the proper consistency.
Use tapioca starch or pearl tapioca to thicken fillings for acidic fruit pies. Acidic fruits often neutralize the thickening characteristics of ordinary flour, but tapioca loses none of its thickening power in acidic environments. Use 3 tbsp. of tapioca for every 1/4 cup you would normally use of flour.
Substitute tapioca flour for cornstarch in sauce and gravy recipes in equivalent amounts. Stir the tapioca in water and add it just before the sauce is finished. Tapioca does not clump like cornstarch and will not break down if you freeze a sauce for reuse later.
If pearl tapioca is the only type you can find and you want a smooth sauce without the gelatinous balls, pulverize the pearls before adding it as a thickener.
Only add tapioca to a sauce after boiling is complete. Tapioca is a low-heat thickener that becomes stringy if boiled. Never heat it beyond a low simmer.