Combine all ingredients in a mixing bowl (or the bowl of a stand mixer with the whisk attachment). Beat at low speed for 1 minute, or until everything is thoroughly combined.
With the mixer running, drizzle ⅓ cup water down the side of the bowl so it doesn't splatter, slowly increasing mixer speed until sugar is incorporated. Beat at medium-high speed for 2 minutes, scraping down the sides as needed.
The icing should be thick and stiff enough so that the beaters or whisk attachment leaves ridges when drawn through.
Divide icing into however many colors you would like and color to your liking and decorate cookies as you would with regular royal icing, watering down slightly to fill piped lines.