If the weather is humid, you may need to beat the frosting for an additional minute in each step to stiffen it. Here, the frosting covers angel food cake and is topped with toasted coconuts.
In the heat-proof bowl of an electric mixer, combine sugar and egg whites. Place the bowl over a pot of gently simmering water, and whisk until the mixture feels warm to the touch and the sugar has dissolved, about 5 minutes.
Return the bowl to the mixer stand. With the whisk attachment, whip on high until cooled, about 8 minutes. Stir in vanilla extract. Use immediately.