Made using only three ingredients, this easy royal icing recipe is great for outlining and flooding sugar cookies, decorating gingerbread houses, adding icing flowers to treats, and other intricate designs. Because this icing hardens as it dries, it’s not usually recommended for cakes and cupcakes, but it’s the perfect hard royal icing for sugar cookies with its smear-proof finish that will keep your fingers icing-free.
Beat all ingredients together until icing forms peaks, about 7-10 minutes at low speed with a heavy-duty mixer or 10-12 minutes at high speed with a hand-held mixer.
Check the consistency of your royal icing. If icing is too stiff, add more water, 1 teaspoon at a time, until desired consistency is achieved. If icing is too thin, add powdered sugar, a little at a time, until desired consistency is achieved.
For stiff consistency: Use 1 tablespoon less water. Stiff royal icing is preferred for making 3-D decorations. With stiffer royal icing, opt for larger piping tips to relieve the pressure on the piping bag.
Medium consistency for icing outlining: Add 1/8 teaspoons of water for every cup of stiff icing. Use a flat utensil like a small angled or straight silicone spatula, to mix icing in a figure-8 motion. Avoid beating or mixing vigorously.
Thin consistency for flooding: To thin for pouring, add 1 teaspoon water per cup of royal icing. Use a grease-free spoon or spatula to stir slowly. Add 1/2 teaspoon water at a time until you reach proper consistency. Use a flat utensil, like a small angled or straight silicone spatula, to mix in a figure 8-motion. Avoid beating or mixing vigorously.
10-second test: Take some icing on a spatula and drop it back down into the bowl to check for the correct thin consistency for flooding. If it sinks after a full count of 10, then the consistency is thin enough for flooding.
Let icing sit for 15 minutes to an hour to let air bubbles rise naturally. Alternately, tap the bowl on the table several times to force the air bubbles up. Gently stir the top surface to release the air.