Royal icing recipe

Ingredients:
225g icing sugar,
sifted 1 egg white
A few drops of rose essence
A few drops of lemon juice

Method:
Beat egg white until it is stiff and frothy.
Add icing sugar, a little at a time and continue beating.
Finally add the rose essence and lemon juice and beat
the mixture until stiff peaks are formed. Use the icing
immediately, otherwise, cover it with a damp cloth to
prevent crusting.
Color the icing as you wish.

source: http://www.creative-cake-decorating.com