This is the only royal icing recipe that I use for cookies, gingerbread houses and fondant cake detail work. It’s easy to work with, sets quickly and doesn’t use raw egg whites. Best of all, it dries just hard enough to paint on and package, but not so hard that it will break a tooth.
In a large bowl using either a hand mixer or a stand mixer fitted with a paddle attachment, beat confectioners' sugar, meringue powder, water and extract (if using) together on medium speed for five minutes. Start the mixer on low to avoid being covered in confectioners' sugar.
I start with six tablespoons of water, but you may need to add more if you live somewhere that is dry, or you like a looser icing for flooding cookies.
When lifting the paddle up, the icing should drizzle down and smooth out within 10-15 seconds. If it's too thick, add more water. If it's too thin, add more sifted confectioners' sugar.
*If you prefer not to use meringue powder, you can omit the meringue powder and the water by replacing them with a total of three pasteurized egg whites (90 grams).
**If you need to make this egg free/vegan, you can omit the meringue powder and water, replacing them with a total of 90 grams aquafaba (six tablespoons).
ChefAlina.com