Royal Icing is that sweet colorful piped icing that dries hard and makes sugar cookies look so good.
The original recipe called for egg whites and powdered (confectioners) sugar, however with so many cases of crazy illnesses being attributed to raw eggs using meringue powder is the best way to go. Meringue Powder can sometimes be found in grocery stores during "cookie baking season" and its almost always in foodie oriented stores such as Willi ams Sonoma and Whole Foods. Craft stores with a cake decorating section often sell meringue powder as well.