Royal icing, which hardens to a glossy, smooth finish, is ideal for decorating cookies like the gingerbread cookies. Royal icing can be made with raw egg whites or with meringue powder (egg whites that have been heated to kill bacteria, dried, and powdered; also called powdered egg whites). Since raw egg whites can, in very rare instances, contain salmonella, the powder is the safest choice. Both of the recipes below make a fairly stiff mixture that’s ideal for piping with a decorating tip. After you pipe outlines, you can thin the remaining icing slightly with water to make icing “paint” for filling in outlines with a brush.
Amazon.com carries the snowflake-shaped cookie cutters for the cookies in the photo. There, you can also find Deb El Just Whites powdered egg whites, which are perfect for making royal icing (it’s also available in most super-markets), and a twelve-color kit of Ateco food coloring gel pastes.