Whole Egg Vanilla Buttercream Frosting

This recipe is from my America's Test Kitchen Cook Book. It is unlike any other frosting I have made before. It doesn't call for any powdered sugar, which I consider a plus.

-Freezing-
I made this frosting several days ahead and froze it. The day before I wanted to use it I put it into the refrigerator to thaw and whipped it up again with my stand mixer before frosting the cake.

Whole Egg Vanilla Buttercream Frosting

4 whole eggs
1 cup granulated sugar
1 tsp. Vanilla extract
Pinch salt
1 pound softened unsalted butter, cut into eighths

Combine eggs, sugar, vanilla, and salt in the bowl of a stand mixer; place bowl over a pan of simmering water. Bring up to 160°F. stirring all the while. The mixture should be thin and foamy.
Remove from heat and, using whisk attachment on your stand mixer, whisk on medium-high speed until cooled down to room temperature, about 5 minutes. The mixture will become light, cream colored, and very fluffy.
Reduce the speed to medium and add softened butter one piece at a time. (After adding half of the butter, the mixture may look curdled; it will smooth with additional butter.)
Once all the butter is added, increase speed to high and beat 1 minute.

Yields: 4+ cups, enough to frost an 8" or 9" round layer cake (2 layers).