Royal icing is so amazing. Beat the crap out of it for 7 minutes and you have this incredibly workable and versatile icing. I use Royal Icing to ice all my holiday cookies at work. When icing cookies with Royal Icing it is important to outline the cookie in some stiff icing first and then flood it with thinned out icing. When thinning your icing be sure to only add a very small amount of water at a time as a little goes a long way. Keep your icing covered at all times as it dried out very quickly and a crust will form, making piping difficult. When outlining your cookie it's up to you what tip you want to use, I generally use bigger tip openings for larger cookies and small tips such as #3 for small cookies. I use meringue powder in my Icing as I don't like using egg whites. You can find meringue powder at the Bulk Barn.
4 cups icing sugar, sifted
1/4 cup meringue powder
1/2 tsp cream of tartar
1/2 cup warm water
Use a stand mixer or a hand mixer for this recipe. In a bowl combine the icing sugar, and cream of tartar. Gently mix to combine. Dissolve the meringue powder in the warm water and add to the icing sugar mixture. Beat on high for 7 minutes. Remove 1/3 of the icing to use for outlining and fine detail decorating. Add a small amount of warm water to the remaining icing until it has been thinned out enough to flood.
Tint your icing with gel food coloring (using liquid food color will thin the icing out too much) and using a pastry bag, outline your cookies. Once the icing outline has hardened a little, flood the cookie with the thinned icing in a pastry bag fitted with a larger tip.Let the icing harden up a bit before you put the finishing touches on the cookies.