The secret to royal icing is in the consistency. Fortunately, royal icing is very forgiving. Does it seem to thick? Add a few drops of liquid at a time to thin it down. Is it too thin? Add a small amounts of confectioners’ sugar and stir until you get it thick enough.
Makes 2 cups
1 pound confectioners sugar, sifted
5 tablespoons meringue powder
1/2 cup of water
Combine all ingredients in the bowl of an electric mixer fitted with the paddle attachment. Mix on low speed until smooth and creamy, about 7 to 10 minutes. If icing is too thick, add more water. If too thin, beat icing 2 to 3 minutes more.
Color icing with desired food colors by blending a drop of coloring into the icing. Gradually blend additional drops until you achieve the desired color.
Fancy Flours: Where Bakers Bloom 
I used this to make 12 doz computer cookies for my son’s wedding instead of a Groom’s cake. The sugar cookies held their shape and the icing stayed consistent. I might add I froze these for 30 days until his wedding and they froze wonderfully and the icing was unaffected.
Could anybody explain me what is meringue powder?
Meringue powder is next to impossible to find. Some of the craft stores stock it but it is a different brand than Fancy Flours carries and it gives the frosting an aftertaste that is not pleasant. Trust me, buy the meringue powder from this website and don’t make any substitutions. Learn from my mistakes ;).