Easy Christmas Cookies With Royal Icing. To make the royal icing: At this point, while the icing is thick, divide it between separate bowls for each color you want.
The secret to beautifully decorated cookies is all in the icing. Once colored, you can further divide each color in two if you plan to use both thick and thin icing to decorate your cookies (more about why you might take this approach in a second) and thin. This royal icing sets or hardens on the iced cookies in about 2 hours' time when sitting on the counter.
To speed this up place the iced cookies in the refrigerator.
An easy sugar cookie icing. To make the royal icing: Divide the icing into smaller bowls and add any desired gel food colors. Makes about four dozen cookies.