Cup of Yum
1. Combine ingredients in the bowl of a stand mixer. If you don't have a stand mixer, you can use a large bowl and a hand mixer. Mix on low speed with a whisk attachment until ingredients are combined (enough that the powdered sugar won't fly everywhere).
2. Turn up the speed to med/high and mix for 5 min or until very thick, shiny, stiff and white. You want the peaks of the icing to stand straight up without flopping over at all.
3. If you want to make several different colors, divide the icing into several different bowls and beat in the food coloring by hand with a rubber spatula.
4. Once you get the correct consistencies for piping (see notes above), place icing in piping bags and start decorating!
5. After icing your cookies, allow cookies to harden at room temperature for at least 12 hours before storing.

To Make Flood Icing:

1. Once you have used all of the royal icing you plan on using (or have set aside the amount of royal icing you need) add about a little of water at a time to the royal icing that you would like to make into flood icing, stirring constantly, until you get the right consistency.
2. You want to be able to pull up a spoonful of icing and have it drip back down into the bowl and combine with the rest of the icing within just a few seconds. You don't want to have it lay on top of the remaining icing for long, you also don't want it to absorb immediately. That means it is too thin. There is a fine line here, which is why you only want to add a little bit of water at a time so you don't overdo it.