This recipe from Stella Parks makes the best royal icing I have ever tasted and decorated with. But that perfection comes with some cost. Ms. Parks is a marvelously scientific baker, and all ingredients are calibrated quite precisely. That means, of course, if you deviate in any way, you may not achieve the perfection she does.
One of this recipe’s strengths is that it starts out on the stovetop, helping to both dissolve the confectioners’ sugar, and cook the egg whites to a safe temperature.
I strongly urge you to put the confectioners’ sugar through a fine mesh sieve or strainer before you measure it, to get absolutely all the lumps out of it before you start. Ms. Parks assumes you will do this, and does not instruct you to do so. Lumpy royal icing is just plain frustrating.
Also, the tiniest bone to pick with the recipe: eggs are not manufactured to factory specifications. They are made by chickens. Every egg is different. “Large” eggs by USDA definition, can be a range of sizes, which means the amount of egg white in each egg is going to be different. Which means you may or may not get enough egg white from two “large” eggs. Which makes the icing a bit stiffer than intended, and necessitates adding more heavy cream in the thinning step.
Ask me how I know.
Have three “large” eggs on hand, and twice the heavy cream the recipe suggests, just in case. Lastly, please, please, please measure the egg whites before putting them in the sugar. If you have excess egg white, you can always toss it into some scrambled eggs in the next day or two.
You will need an instant read thermometer to make this recipe. It really helps.
The link to the recipe is below: