Tapioca pudding always has a delightful texture thanks to the little tapioca pearls in it. But the latest version developed in our test kitchen is off the charts: miraculously light and frothy, with enough body so that the pearls stay aloft rather than sinking to the bottom, as they sometimes do. The secret? A cunning boost of meringue folded into the custardy pudding once it has cooled.
Making a meringue that will function as a sort of airy architecture for the dessert isn't difficult, but it does require your full attention. What you're trying to achieve as you whisk the egg whites and the sugar is twofold. First, you want to beat in air until it unwinds some of the tightly wound egg proteins, which will bond together around bubbles of air. Then, you want to make sure the new structure remains intact; that's where the sugar comes in. It will dissolve and form a syrup that will coat and reinforce the unfurled proteins.
Success comes down, in large part, to when you introduce the sugar. If you add it too early you'll end up whisking and whisking without gaining any volume. For the lightest, highest meringue, wait until soft peaks just begin to form in the egg whites—that indicates that the air bubbles are close to the size you want to capture—then add the sugar, and continue working the meringue to the point at which stiff peaks form. That means the bubbles have subdivided to form a tighter structure that will hold together in the pudding, making it the fluffiest you've ever eaten.