Seven-Minute Frosting

Method - Combine and beat all ingredients except the vanilla: In a large metal or heatproof glass bowl, combine the sugar, water, egg whites, corn syrup, cream of tartar, and salt. Beat with an electric hand mixer at low speed just to combine so the eggs are lightly frothy.

Method - Set up your double boiler: Fill a medium saucepot about 1/3 of the way with water. Set it over medium to medium low heat and bring it to a moderate simmer not a boil. The water should have small to medium-sized steady bubbles on the edges of the pot. You do not want the simmering water in the saucepot to touch the bottom of the bowl. You are using the steam to cook the frosting, not the water directly. The greatest danger with this frosting is cooking it over too high of heat.

Method - Beat the frosting: Use a hand mixer to beat the mixture at low speed; over the next 3 minutes, gradually increase the speed to high. The first minute or so, the mixture will be frothy, with large bubbles. After 2 to 3 minutes, the mixture will be foamy, with finer bubbles. Around 4 to 5 minutes, it will have greatly increased in volume and will be fluffy, and white like soft clouds. Around 5 to 7 minutes, the beaters will leave very distinct trails in the frosting. It will be glossy, stiff, and sticky. If you lift the beaters from the bowl, they'll form firm little peaks in the frosting. Keep beating and cooking until you see the peaks—it might take a little less or more than 7 minutes.

Method - Remove the frosting from heat and let cool: Remove the bowl from the double boiler. Continue beating until the icing is very stiff and glossy, another 2 to 3 minutes (this increases the volume of the frosting, but also helps it cool down). Stir in the vanilla extract.

Method - Use the frosting: Use the frosting within 30 minutes. As it sits, the frosting becomes too tacky and deflated to work with. If someone comes to the door and you can't use the frosting immediately, drape a warm, damp kitchen towel over the bowl. This can buy you a little time.

Method - Serve: Cakes with this frosting are best enjoyed the day they are decorated; after about 4 hours, the frosting will look less glamorous and become tacky, with a chalky outer crust. It's still safe and delicious to eat. It's just not very pretty.

Method - Store cakes uncovered: Store cakes iced with seven-minute frosting uncovered and avoid having plastic wrap come into contact with the frosting—it'll stick to the wrap. If your cake is sliced you can fold plastic wrap or parchment over and press it against the cut part of cake to prevent it from drying out.