Coffee Frosting

A thin poured glaze rather than a spreadable buttercream, meant to be used while still warm enough to flow. The whole thing takes about five minutes and depends on temperature control more than technique.

• Keep it lukewarm, not hotThe instruction to set the bowl over hot water is the hinge of the recipe. Too cool and the mixture stiffens and drags as you spread it; too warm and it thins and runs off. Aim for barely warm to the touch and work quickly.
• Strong coffeeRead this as coffee brewed noticeably stronger than for drinking, not espresso. Two tablespoons of strongly brewed drip coffee, or a scant two tablespoons of hot water with a half teaspoon of instant coffee stirred in, both work.
• Corn syrup's jobThe half tablespoon of syrup is an anti-crystallising agent, not a sweetener. It keeps the glaze glossy and stops it drying chalky. Golden syrup or glucose substitute directly; honey will work but adds flavour.
• Confectioners' sugarModern confectioners' sugar contains cornstarch, which period sugar may not have. Sift it as directed regardless, since lumps will not beat out in a mixture this thin.
• Add gradually, and stop when it coatsThe tablespoon-at-a-time method lets you judge consistency. One and a quarter cups is a target, not a rule; stop when the glaze ribbons off the spoon and holds a line for a second or two.
• YieldA small quantity: enough to cover the top of a single small cake or a few little cakes. Double it if you want to coat the sides as well.
• SettingIt firms to a soft sheen as it cools and stays somewhat tacky; the corn syrup discourages a hard, dry crust, so let glazed cakes dry before stacking or covering them.