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 to 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 to room temperatur e and beat until smooth with the machine. Beat in flavoring, a little at a time, and continue beating until buttercream is smooth, about 2 minutes longer (always flavored buttercream immediately before using it.) Flavorings: Liqueur: 2 to 3 tablespoons liqueur (such as Grand Marnier or dark or light rum) Lemon: 2 to 3 tablespoons lemon juice Coffee: 3 tablespoons instant coffee (espresso, if possible) dissolved in 2 tablespoons water, coffee or rum Raspberry: 3/4 cup raspberry puree made by cooking down and straining a 10-ounce package of frozen raspberries Recipe by: Cooking Live Show #CL8876 Posted to MC-Recipe Digest V1 #606 by "Angele and Jon Freeman" on May 12, 1997