-
1
Set a medium-fine strainer over the bowl of a stand mixer with the paddle attachment.
-
2
In a medium stainless steel bowl (because glass bowls are too slow to heat), whisk the egg yolks (or whole eggs), salt, and water together thoroughly. Whisk in the sugar.
-
3
Set the bowl in a wide skillet filled with enough hot water to reach above the depth of the egg mixture. Over medium heat, with a heatproof silicone spatula, stir the egg mixture, sweeping the sides and bottom of the bowl constantly to prevent the eggs from scrambling. Adjust the burner so the water barely simmers and continue to stir until the mixture registers between 175u00b0 F and 180u00b0 F on an instant-read thermometer. Swish the thermometer stem in the hot skillet water to rinse off the raw egg after reading the temperature each time.
-
4
Remove the bowl from the skillet and scrape the mixture into the strainer. Rap the strainer to coax the mixture through it, but do not press on any bits that are left in the strainer. Turn the strainer and scrape the mixture clinging to the underside into the bowl of the stand mixer. Beat with the paddle attachment on high speed for 3 to 5 minutes, or until the mixture is cool and resembles a fluffy, foam-like soft whipped cream.
-
5
Beat the butter into the foam a tablespoon at a time. The foam will deflate as you add the butter. If the butter is a little too cold, the mixture may curdle or separate at first, but it will smooth out as you continue to beat, and if it doesn't you can set it in the warm water in the skillet for a few seconds and then continue to beat. If the foam is still warm or the butter too soft when you combine them, the buttercream will seem a little soupy instead of thick and creamy. If it doesn't come together and thicken with beating, set the bowl in a bowl of ice and water or in the refrigerator for 5 to 10 minutes; then resume beating until the mixture is creamy and smooth.
-
6
Use the buttercream right away or refrigerate it until needed. Buttercream keeps in a sealed container in the refrigerator for several days or in the freezer for 3 months. To soften, break chilled or frozen buttercream into chunks with a fork. Microwave on low for just a few seconds, then stir with a rubber spatula. Or set the bowl in hot water until some buttercream melts around the sides of the bowl. Remove the bowl and stir. If the buttercream is not smooth and spreadable, repeat the gentle warming and stirring steps until it is.
