Dessert & Treats Recipes Cake Recipes Fillings & Frostings Buttercream Frosting Recipes Swiss-Meringue Buttercream for Block and Bootie Cakes Be the first to rate & review! By Martha Stewart Test Kitchen Martha Stewart Test Kitchen The recipes developed by our test kitchen team have undergone a rigorous process of development and testing, ensuring that every element is optimal, from ingredient amounts to method and cooking time. This process includes triple-testing recipes to ensure they meet our high standards. The many stellar cooks and food editors who have been part of our team include Sarah Carey, Lucinda Scala Quinn, Jennifer Aaronson, Shira Bocar, Anna Kovel, Greg Lofts, Riley Wofford, Lauren Tyrell, and Lindsay Leopold. Editorial Guidelines Updated on September 28, 2016 Print Rate It Share Share Tweet Pin Email Yield: Makes about 10 1/2 cups Use this recipe when making our Block Cakes and Bootie Cakes. Ingredients 3 ½ cups sugar 14 large egg whites, or packaged whipping-quality egg whites 4 ½ cups (9 sticks) unsalted butter, softened, cut into tablespoons 2 teaspoons pure vanilla extract Directions In a heatproof mixing bowl set over a pot of simmering water, whisk together the sugar and egg whites until sugar has dissolved and mixture is warm, 2 to 3 minutes. Remove bowl from heat. Using an electric mixer, beat egg-white mixture on high speed until fluffy and completely cooled, about 10 minutes. With mixer on low speed, add the butter, a tablespoon at a time, beating until fully incorporated after each addition. (Don't worry if your buttercream appears curdled after all the butter has been added; continue beating until smooth again.) Add the vanilla extract, and beat until combined. If using buttercream the same day, let stand at room temperature, covered tightly with plastic wrap. When tinting buttercream, add food coloring a drop at a time, and stir well before adding more. Cook's Notes Transfer buttercream to an airtight container, and refrigerate up to 5 days; before using, bring to room temperature, and beat until smooth, about 10 minutes. Do not tint before storing, as color tends to fade. Rate it Print