The marshmallow-like flavor and consistency of seven-minute frosting can't be beat when you're in the mood for a little nostalgia with your cake. Touted as a foolproof recipe for many decades, it is actually anything but foolproof. With so few steps, technique and patience are crucial to seven-minute frosting's success. Give yourself some time to master the techniques, and you will be rewarded with a wonderfully fluffy white frosting adorning your cake.
Pour 1 quart water into a 4-quart pot, and bring the water to a boil over high heat. Reduce the heat to medium to maintain a simmer. Pay close attention to the amount and temperature of the water in the pot, as both need to be just right to ensure success.
Separate two eggs, placing the whites in a medium bowl. Discard the yolks or reserve them for a different application -- yolks are not used to make this frosting. Use eggs taken directly from the refrigerator, as opposed to eggs that have been sitting at room temperature. Cold eggs are much easier to separate, which minimizes the risk of getting yolks mixed in with the egg whites -- yolks prevent this frosting from whipping up properly and make the frosting runny.
Place 1 1/2 cups sugar, 1/3 cup cold water, 1/2 tsp. cream of tartar and a pinch of salt into the bowl with the egg whites. Cream of tartar is an acid and helps ensure the egg whites beat up to a strong, fluffy consistency.
Set the bowl with your ingredients over the pot of simmering water. Immediately beat the mixture with a hand-held mixer on low for one minute. If the water is touching the bottom of the bowl or is too hot, you will overcook the egg whites, and your frosting will not whip up sufficiently.
Turn the mixer on high, still beating the egg whites for an additional five minutes. After five minutes, the result should be hot, shiny, stiff-peak egg whites in your bowl. You may need additional time to achieve the proper results, but your patience will be rewarded.
Remove the bowl from the heat, add 1 tsp. vanilla extract and continue to beat the frosting on high for an additional minute. Let the frosting stand for 30 minutes before using it to ensure that the frosting is cool enough to cover your cake without sliding off.