Chef
Boiled icing is a type of dessert topping whose base is made primarily by boiling sugar with other ingredients to form a thick, sticky substance. The boiled ingredients are then gradually whisked together with the egg whites, which incorporate air into the mixture to result in a light, fluffy icing. Icing is often used to cover cakes, cupcakes, and other desserts, but it’s considered too gooey and light to use for decorative piping or other intricate designs.
The base of boiled icing tends to consist mostly of granulated sugar, with small amounts of salt and cream of tartar. The salt is thought to enhance the other flavors of the topping and draw more moisture from the other ingredients so that the final product is satiny and spreadable. Cream of tartar, scientifically known as potassium hydrogen tartrate, is a type of acidic salt that is believed to stabilize and increase the volume of whipped egg whites in icing. Many also find that it gives a smooth texture to the icing, preventing the sugar from crystallizing and hardening.
Boiled topping is usually made by combining about 1.5 cups (192 grams) of sugar, a pinch of salt, and ½ teaspoon of cream of tartar with cold water. Recipes generally vary in the amount of water needed, but can range from 0.25 cups to 0.50 cups (32 to 64 grams). The mixture is then cooked on a stove over medium heat until smooth and thick, reaching about 240 degrees Fahrenheit (115.56 degrees Celsius). Egg whites are usually beaten until they become soft and fluffy peaks and then beaten while the boiled sugar mixture is slowly poured into the whites. The whole mixture is beaten until a smooth and shiny consistency is obtained.
Since boiled icing tends to be sticky, it is generally recommended to use it as soon as possible. To prevent crumbs from mixing with the frosting, recipes may recommend applying large amounts of frosting to the middle of the dessert and spreading from the center. This type of icing is often used to make a spiral design on desserts by applying the icing in a thick, even layer, then using the back of a spoon to make several circular motions to form swirls. While it’s a good idea to use boiled icing immediately after making it for best results, it can also be covered tightly and stored in the refrigerator up to a day before using. If not covered well or stored for more than a day, the frosting may start to harden and not spread.