Dessert & Treats Recipes Cake Recipes Fillings & Frostings Buttercream Frosting Recipes Buttercream Frosting 2.8 (92) 2 Reviews 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 May 16, 2017 Print Rate It Share Share Tweet Pin Email Yield: 8 cups Ingredients 2 cups sugar 6 large egg whites Pinch of salt ½ teaspoon cream of tartar 1 ¼ pounds (5 sticks) unsalted butter, room temperature ¼ cup Grand Marnier or 1 tablespoon pure vanilla extract Directions In a small, heavy-bottomed saucepan, mix together sugar and 2/3 cup water. Bring to a boil and do not stir. Cover and boil until no sugar crystals remain, 2 to 3 minutes. Uncover and continue boiling until syrup reaches 240 degrees on a candy thermometer (soft-ball stage). Meanwhile, in the bowl of an electric mixer fitted with the whisk attachment, beat together egg whites and cream of tartar until stiff peaks form. When sugar mixture has reached 240 degrees, add 1/4 cup to bowl of mixer, drop by drop. Slowly add remaining sugar mixture and continue beating until cool, 7 to 10 minutes. In the clean bowl of an electric mixer fitted with the paddle attachment, cream butter until fluffy. Add creamed butter to cooled egg white mixture, 3 tablespoons at a time, whisking well after each addition. Frosting should become thick and creamy. If egg mixture is too warm, frosting may remain thin; set bowl over ice and stir until thickened. Add Grand Marnier and mix until well combined. Use frosting immediately. Rate it Print