Food & Cooking Recipes Mocha Buttercream and Mocha Pastry Cream 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 June 12, 2017 Print Rate It Share Share Tweet Pin Email Photo: Sang An Prep Time: 45 mins Total Time: 3 hrs 5 mins Yield: Makes 4 cups each (enough for one 8-inch layer cake) A filling of custardy pastry cream is layered within the Mocha Bubble Cake. Ultra-smooth buttercream adds a rich finishing touch. Ingredients For the Mocha Buttercream 2 tablespoons instant espresso powder 2 tablespoons hot water 4 large egg whites, room temperature 1 ¼ cups sugar 3 sticks unsalted butter, room temperature, cut into small pieces 5 ounces semisweet chocolate, coarsely chopped, melted and cooled For the Mocha Pastry Cream 2 ½ teaspoons instant espresso powder 2 ½ teaspoons hot water 2 large eggs, plus 2 large egg yolks ½ cup sugar ½ cup whole milk ½ vanilla bean, split and scraped, pod reserved for another use ¼ cup plus 1 ½ teaspoons cornstarch Salt 1 ½ tablespoons unsalted butter, cut into small pieces 1 ½ ounces bittersweet chocolate, coarsely chopped Directions Make the mocha buttercream: Combine espresso powder and hot water in a small bowl; stir until espresso dissolves. Heat egg whites and sugar in a heatproof bowl of a mixer set over a pan of simmering water, whisking until whites are warm to the touch and sugar dissolves, 2 to 3 minutes. (Mixture should feel smooth when rubbed between 2 fingers.) Whisk egg-white mixture with a mixer on medium-high speed until stiff, glossy peaks form and mixture cools completely, about 10 minutes. Reduce speed to medium-low. Add butter, a few tablespoons at a time, whisking well after each addition. Switch to the paddle attachment, and reduce speed to low. Beat in espresso mixture and melted chocolate until smooth, then beat to reduce air bubbles, 3 to 5 minutes. Cover with plastic wrap, and let stand at room temperature until ready to use. Make the mocha pastry cream: Prepare an ice-water bath. Combine espresso powder and hot water in a small bowl; stir until espresso dissolves. Whisk eggs, egg yolks, and 1/4 cup sugar in medium bowl. Bring remaining 1/4 cup sugar, the milk, vanilla seeds, cornstarch, and 1/4 teaspoon salt to a boil in a medium saucepan over medium-high heat, whisking constantly. Remove from heat, and gradually whisk one-third of hot-milk mixture into egg mixture. Whisk entire mixture back into saucepan. Raise heat to medium-high, and bring to a boil, whisking constantly. Cook, continuing to whisk, until mixture is thick enough to hold its shape when lifted with a spoon, about 3 minutes. Remove from heat. Whisk in butter, 1 piece at a time. Whisk in espresso mixture and chopped chocolate until smooth. Strain mixture through a fine sieve into a bowl. Cover with parchment or plastic wrap, pressing it directly on surface to prevent a skin from forming. Transfer to ice-water bath; let stand until cooled, about 30 minutes. Refrigerate until chilled and firm, at least 2 hours. Rate it Print