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 a hand mixer or a stand mixer fitted with a paddle attachment, beat all of the icing ingredients together on medium speed for 5 minutes - start the mixer on low to avoid being covered in powdered sugar.
I start with 6 Tablespoons of water, 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 off the icing, 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.
When you're not working directly with the royal icing (for example, if you are dividing your icing to make multiple colors), place a damp paper towel directly on the surface of the royal icing. This prevents it from hardening.
This icing dries in about 2 hours at room temperature but I usually leave my cookies to dry 8 hours or overnight if I am packaging them for gifts or for children to decorate with edible markers.