This buttercream was one of the components to my plated desserts that I had to make for my practical finals during the baking & pastry phases in culinary school. It is extremely light and soft, and is based on an Italian meringue (as you're cooking the egg whites with hot sugar syrup). If prepared right, it is a beautiful shiny white buttercream that's just sweet enough (not overly sweet).
*All ingredients should be at room temperature before beginning.
Place the egg whites in a dry, grease-free mixer bowl. Have 9 ounces of the sugar nearby.
Place 9 ounces of the sugar in a heavy saucepan with enough water to moisten. Bring to a boil over high heat.
As the sugar syrup's temperature approaches the soft ball stage (240°F.), begin whipping the egg whites. Watch the sugar closely so that the temperature doesn't exceed 240°F.
When soft peaks form in the egg whites, gradually add the remaining 4 1/2 ounces of sugar to them. Reduce the mixer speed to medium and continue whipping the egg whites to stiff peaks.
When the sugar syrup reaches the soft ball stage, immediately pour it into the whites while the mixer is running. Pour the syrup in a steady stream between the side of the bowl and the beater. If the syrup hits the beater, it will splatter and cause lumps. Continue beating at medium speed until the egg whites are completely cool. At this point, you have Italian meringue.
Gradually add the softened butter to the Italian meringue and continue whipping until all of the butter is incorporated. Add flavoring, if desired.
CHOCOLATE ITALIAN BUTTERCREAM
Add 1/4 oz vanilla extract to the buttercream, then stir in 5 oz of melted and cooled bittersweet chocolate.
LEMON ITALIAN BUTTERCREAM
Add 1 fl oz of lemon extract and 1 tablespoon grated lemon zest to the buttercream.
COFFEE ITALIAN BUTTERCREAM
Add 1 fl oz coffee extract or strong coffee to the buttercream.