That from reader Victor on the tempered chocolate glaze recipe below, which calls for a small amount of clarified butter. The reason has to do with the “fat bloom” I mentioned yesterday. Just as a refresher, fat bloom is what frequently happens when melted chocolate isn’t tempered properly, then re-solidifies. The random, unstable crystal formation causes additional liquid cocoa butter to leech out of the chocolate and crystallize on the surface of the mass. It’s a phenomenon just about everyone has seen: those gray streaks.
Clarified butter provides extra insurance against fat bloom by introducing different kinds of fat molecules to the mixture (dairy fat as opposed to cocoa fat). The dairy fat molecules have a different shape than the cocoa fat molecules, and so interfere with the cocoa butter’s ability to form crystals. It’s like adding a bunch of Lincoln Logs to a mass of LEGOs. The two just don’t fit together. Of course, properly tempered chocolate doesn’t bloom. But then we’re not all — ehem — precision chocolatiers.