Special equipment: an electric mixer or heavy-duty mixer fitted with a wire whisk attachment
Combine all ingredients in the bowl of an electric mixer fitted with the whisk attachment. Start on slow speed and whisk the mixture and as the mixture begins to come together increase the speed. Mix for 6 to 8 minutes or until fluffy and shiny; it may be necessary to scrape down the sides of the bowl with a rubber spatula after the first 3 minutes so that all the ingredients can be fully incorporated. Keep covered with a damp towel until ready to use (see Cook's Note*).
Use to decorate gingerbread houses and cookies.
*Meringue powder can be purchased at health and bulk food stores. It may also be called dried egg whites. The royal icing can vary depending on the brand of meringue powder used and the humidity; it may be necessary to thin the icing with an additional tablespoon of warm water or thicken it with additional icing sugar to make the desired consistency. If the icing is going to be used for piping, it should be thinned to the consistency of molasses.