Dessert & Treats Recipes Cake Recipes Fillings & Frostings Buttercream Frosting Recipes Make-Ahead Swiss Meringue Buttercream 3.4 (154) 6 Reviews By Martha Stewart Editors Martha Stewart Editors Facebook Instagram Twitter Website An article attributed to "Martha Stewart Editors" indicates when several writers and editors have contributed to an article over the years. These collaborations allow us to provide you with the most accurate, up-to-date, and comprehensive information available.The Martha Stewart team aims to teach and inspire readers daily with tested-until-perfected recipes, creative DIY projects, and elevated home and entertaining ideas. They are experts in their fields who research, create, and test the best ways to help readers design the life they want. The joy is in the doing. Editorial Guidelines Updated on November 16, 2017 Print Share Share Tweet Pin Email Yield: 6 cups Ingredients 1 pound (4 sticks) unsalted butter, room temperature 1 ½ cups sugar 6 egg whites 1 teaspoon pure vanilla extract Directions Beat butter with electric mixer until fluffy and pale. Transfer to small bowl. In double boiler over simmering water, whisk sugar and egg whites until warm and sugar is dissolved, 2 to 3 minutes. Transfer to clean bowl of electric mixer; beat on high with whisk attachment until fluffy and cooled, about 10 minutes. Reduce mixer to medium-low; add butter a scant 1/4 cup at a time, beating well after each addition. Mix in vanilla. Switch to paddle attachment; beat on lowest speed 3 to 5 minutes. Leave at room temperature if using same day. Cook's Notes Store airtight in refrigerator up to 3 days. Bring to room temperature; beat until smooth. Print