Royal Icing is an excellent icing to use for highly decorative baked goods and confections but not the best thing to use for frosting cakes.  Because Royal Icing sets up had it is perfect to use for decorating such things as gingerbread houses, decorations on wedding cakes, Day of the Dead sugar skulls and panoramic Eggs.  I have always used egg whites, however some people prefer to use meringue powder which can be obtained at baking and candy making specialty shops. 

Making Royal Icing is not rocket science.  The recipe is simple, 1 raw egg white to each cup and one half of powdered sugar, and enough cold water to achieve the consistency you wish.

Sift the powdered sugar.  Lightly whip the egg white using a table fork.  Combine the two and mix with an electric rotary beater on the low speed until the mixture is smooth and glossy.  Add cold water a few drops at a time to achieve the consistency you wish.  If you are going to be adding food coloring, remember that is will thin the mixture as well, so you may want to add the water after you have added the food coloring.   

The icing will become quite hard as it sits.  If you are working on a project that will take some considerable time, cover your bowls of icing with plastic wrap to prevent the surface from forming a crust.