Only 3 ingredients- and they are common household ingredients too!
All you need is:
2 large egg whites
2 teaspoons fresh lemon
3 cups powdered sugar, sifted
Beat the egg whites with the lemon juice until combined, and then gradually add the powdered sugar.
You’ll know your frosting is ready to use when you drizzle a “ribbon” and it remains on the surface for a few seconds. You want it to be thick enough so that when you put it on your cookies (or whatever) it won’t run off the edge, but stay in place.
If it isn’t thick enough, you can always add more powdered sugar. However you don’t want to beat it too much or the eggs will get whipped to much and give your frosting a curdled texture.
Add a little color to your frosting with food coloring. But remember that a little goes a long way, and you can always add more.
Use your Royal Icing right away. It hardens when exposed to air very quickly (which makes it both wonderful but sometimes hard to use!)
If you are not going to use it right away, then store it in an airtight container immediately.