
This is called a meringue buttercream because its foundation is egg whites, not the more traditional yolks. That makes it very light, satiny, and easy to spread—a plus if you're making a many-layered cake like the one in the preceding recipe. The base for this buttercream yields two different-flavored frostings: espresso coffee and bittersweet-chocolate mocha.
•If buttercream looks soupy after some butter is added, meringue is too warm: Chill bottom of bowl in an ice bath for a few seconds before continuing to beat in remaining butter.
•Buttercreams can be made 1 week ahead and chilled or 1 month ahead and frozen. Bring to room temperature (do not use a microwave), about 2 hours, and beat with an electric mixer until spreadable.
•The egg whites in this recipe are not fully cooked.
