Gateau Concorde - Prepare from Scratch

      The structure of this cake is surprisingly straightforward: it consists of three layers of chocolate meringue, layered with and surrounded by chocolate mousse, and topped with a coating of broken meringue strips that provide its unique texture. Cocoa powder and powdered sugar are gradually folded into the whipped egg whites in three separate stages until just mixed. Overmixing can cause the meringue to lose volume and spread, while undermixing may leave cocoa streaks that bake inconsistently. However, there's no need to be daunted! Meringue is more forgiving than it is often thought to be. Pipe the strips with consistent pressure, allowing them to naturally drop from the bag instead of pressing them flat—this helps maintain their round shape and ensures even baking.

      Makes 1 (8-inch) cake

      Meringue: 2 cups (240 grams) confectioners’ sugar, 1 cup (85 grams) unsweetened cocoa powder, 8 large egg whites (240 grams), at room temperature, 1¾ cups (350 grams) granulated sugar, ¼ teaspoon kosher salt.

      Mousse: 6 ounces (170 grams) 64% cacao bittersweet chocolate, chopped, 3 tablespoons (45 grams) heavy whipping cream, at room temperature, 4 large egg whites (120 grams), at room temperature (see Note), ¼ teaspoon kosher salt, 10 tablespoons (120 grams) granulated sugar, 1¾ cups (420 grams) cold heavy whipping cream.

      For the meringue: Preheat the oven to 225°F (105°C). Using a dark marker, draw 2 (8-inch) circles on a sheet of parchment paper, placing it ink side down on a baking sheet. Draw another 8-inch circle on a separate sheet of parchment paper, and lay it ink side down on another baking sheet. In a medium bowl, combine confectioners’ sugar and cocoa. In the stand mixer bowl fitted with the whisk attachment, beat the egg whites on medium speed until soft peaks form, about 3 to 4 minutes. With the mixer running on medium speed, slowly add granulated sugar in a steady stream; increase the speed to medium-high, and beat until stiff peaks form and the sugar has completely dissolved, about 4 to 5 minutes. Sift the confectioners’ sugar mixture over the egg whites in three parts, folding gently after each addition until just combined. Transfer the meringue to a pastry bag fitted with a ½-inch round piping tip (Ateco #806). Starting at the center of each drawn circle, pipe the meringue in a spiral to fill each circle. Use the remaining meringue to pipe long strips in the available space on the baking sheets. (Maintain even pressure on the pastry bag and allow the meringue to fall naturally from the bag to keep its tubular shape. Avoid making the strips too thin or too thick, as this can cause uneven baking.) Bake until completely dry and set, and the meringue strips can be easily lifted away from the parchment, about 1 hour. Turn off the oven and let the meringues cool in the oven for 1 hour. Once cooled, store the meringues in an airtight container for up to 2 days.

      For the mousse: In a double boiler, melt the chocolate over simmering water while whisking frequently. Remove from heat and whisk in the room temperature cream. In the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites and salt on medium speed until soft peaks form. Gradually add granulated sugar while the mixer is on medium speed; increase the speed to medium-high and beat until stiff peaks form, about 3 to 4 minutes. Transfer this mixture to another bowl. In the bowl of a stand mixer fitted with the whisk attachment (you don’t need to clean it between uses), beat the cold cream on medium speed until stiff peaks form. Fold the whipped cream into the chocolate mixture until combined, then add the egg white mixture, folding until no streaks remain. Use the mousse immediately.

      To assemble, remove the cooled meringue strips from the parchment paper. Using a sharp paring knife, cut the meringue strips into 2-inch pieces. With a large offset spatula, place one meringue disk on your chosen serving platter. Spread 1½ cups (about 270 grams) of mousse on top of the meringue. Add the second meringue disk, followed by another 1½ cups (about 270 grams) of mousse. Place the final meringue disk on top, then spread the remaining mousse over the top and sides of the cake. Arrange the meringue strip pieces on the top and sides of the cake as desired. Refrigerate for at least 4 hours or overnight before serving. (The extended chilling helps soften the meringue layers, making them easier to slice.)