One of the best-tasting buttercreams is also the easiest to prepare. See the end of the recipe for flavoring possibilities.
Easy Meringue Buttercream
4 large egg whites (1/2 cup)
1 cup sugar
12 ounces (3 sticks) unsalted butter, softened
Place egg whites, sugar and salt in medium-sized heatproof mixing bowl over a pan of simmering water and whisk gently and constantly until egg whites are hot (about 140 degrees) and sugar is dissolved, about 3-4 minutes.
Remove from heat and whip by machine until thick and cooled, about 5 minutes. Beat in butter and continue beating until buttercream is smooth and spreadable.
Use immediately or refrigerate, covered, for up to 5 days.
Before using, bring buttercream to room temperature and beat smooth by machine.
Beat in flavoring, a little at a time, and continue beating until buttercream is smooth, about 2 minutes longer (always flavor buttercream immediately before using it.)
Liqueur: 2-3 Tbsp. liqueur, such as Grand Marnier or dark or light rum.
Lemon: 2-3 Tbsp. lemon juice.
Coffee: 3 Tbsp. instant coffee (espresso, if possible) dissolved in 2 Tbsp. water, coffee or rum.
Raspberry: 3/4 cup thick raspberry puree made by cooking down and straining a 10-ounce package of frozen raspberries.
Chocolate: 6 ounces chocolate melted with 4 Tbsp. water, coffee or milk and cooled.