Another confession. We're not really fans of powdered sugar. It's messy, has a weird metallic flavor, and often leaves a gritty texture in frosting. Oh, it's fine for a quick dusting on pastry. But as the main ingredient of a quick buttercream, it's too sweet, too gritty - and liable to be scraped off at our house.
The culprit for these complaints is cornstarch, which is added to powdered sugar to keep it from caking. According to a great article from Serious Eats, cornstarch is the least hydroscopic all all starches, meaning it doesn't attract water and keeps the sugar soft and free-flowing. Best of all for sugar manufacturers, it is readily available and cheap.
If you've ever sampled cornstarch, you know it has an unpleasant chalky taste and texture (we tasted it in the name of science). It's not soluble at room temperature (like in a frosting); only at temperatures near boiling will it dissolve and become incorporated into your dish.
So what's a baker to do?
We recommend you get an organic powdered sugar that uses tapioca, ground from a cassava root. Even if you are not concerned about GMOs, you'll love its neutral to sweet flavor, and its ability to thicken at room temperature. Not only does tapioca-based powdered sugar feel creamier and smoother, it can help add body to no-cook desserts.
Best of all, you'll need a lot less organic tapioca-based confectioner's sugar for a batch of smooth, silky American buttercream frosting.
That's important, because tapioca-based organic powdered sugar is painfully expensive and not as readily available at local groceries. The brands we've tried are Wholesome Yum ($5-6) and Trader Joe's organic ($3) for a one pound bag.
So we'll understand if you save it for special occasions.
If you'd like more information about confectioner's sugar or to see the original Serious Eats article, click here