Once you've whipped up a batch of royal icing, it will fairly quickly form a crust and start setting if you leave it in the open air. Here is a simple trick to prevent your icing from drying out while you're decorating a big batch of cookies. Once you've coloured your icing, place a very damp paper towel directly on top of the icing. Make sure all exposed areas of icing are in direct contact with the paper towel. This will keep the top of the icing moist. Once you're ready to use the icing again, vigorously stir with a spoon until perfectly smooth and decorate away! Photography by Jennifer Bartoli