“Many years ago, when my parents moved from New York City upstate to Grafton, New York, my mother reported with great excitement that they had discovered an amazing bakery in Saratoga Springs called Mrs. London’s. After I had visited the bakery and was treated to an array of just about every fabulous dessert on the menu, this simple mousse cake is the one that I was most moved to recreate.” – Rose Levy Beranbaum
Heavenly Chocolate Mousse Cake
Serves 8 to 10
Oven Temperature: 450°F/230°C
Baking Time: 7 to 10 minutes
A gossamer soft and delicate sponge cake (biscuit) is cut to fit and line a loaf pan that is then filled with an equally ethereal and deliciously mellow and velvety chocolate mousse.
Plan Ahead: The sponge cake (biscuit) can be baked, cooled, and placed in the pan while the chocolate custard is cooling before you complete the mousse. Alternatively, the cake can be made a day ahead.
For the cake: See Light Sponge Cake (Biscuit).
For assembling the cake: One 8½ by 4½ inch (6 cups) loaf pan.
One baking sheet or extra half sheet pan (inverted), lightly coated with nonstick cooking spray.
Light Sponge Cake (Biscuit)
Makes 16¾ by 11¾ by ½ inch rectangle
This versatile cake, which is used in varying ways for several recipes throughout the book, takes about 10 minutes to mix and 10 minutes or less to bake. It is a slender, airy, yet velvety cake layer containing no fat other than that from the egg yolks, making it sturdy enough to absorb moisture from other components without falling apart. The following recipe gives instructions for baking the cake in a half sheet pan. The cake can also be made in two 10 inch round cake or 9½ inch round tart pans, which are ideal for making two round cake bases. One base can be used for the recipe, while the other can be frozen for future use. Individual recipes will specify modifications to this recipe.
One 17¼ by 12¼ by 1 inch half sheet pan, bottom coated with shortening, then lined with parchment (cut the parchment to extend 1 inch past one of the long sides of the pan) coated with baking spray with flour
One large uncoated wire rack
One baking sheet or extra half sheet pan (inverted), lightly coated with nonstick cooking spray
1/2 cup (or 1/4 cup plus 2 teaspoons) 1.2 ounces or 33 grams bleached cake flour (or bleached all-purpose flour) sifted into the cup and leveled off
2-1/2 or 22 grams tablespoons Corn starch
5 (to 8) large eggs, separated, at room temperature — yolks (1/4 cup plus 2 tablespoons) 3.3 ounces or 93 grams; whites (about 4) – 1/2 cup (118 ml), divided (4.2 ounces or 120 grams)
1/2 cup plus 1 Tablespoon, divided superfine sugar (4 ounces or 113 grams)
¾ teaspoon (3.7 ml) pure vanilla extract
1/4 teaspoon (0.8 grams)
Preheat the Oven Thirty minutes or longer before baking, set an oven rack in the middle of the oven and preheat the oven to 450°F/230°C.
Mix the Dry Ingredients In a small bowl, whisk together the flour and cornstarch until well combined.
Mix the Egg Mixture In the bowl of a stand mixer fitted with the whisk beater, place the egg yolks, half of the egg whites (¼ cup/59 ml/2.1 ounces/60 grams), and ½ cup/ 3.5 ounces/100 grams of the sugar. Beat on high speed until thick, fluffy, and tripled in volume, about 5 minutes. Lower the speed and beat in the vanilla. If you don’t have a second mixer bowl, scrape this mixture into a large bowl and thoroughly wash, rinse, and dry the mixer bowl and whisk beater to remove any trace of oil.
Make the Batter Sift half of the flour mixture over the egg mixture and, using a large balloon whisk, slotted skimmer, or silicone spatula, fold it in gently but rapidly until almost all of the flour has disappeared. Repeat with the remaining flour mixture until all traces of the flour have disappeared.
Beat the Egg Whites into a Stiff Meringue In the bowl of a stand mixer fitted with the whisk beater, beat the remaining egg whites and the cream of tartar on medium-low speed until foamy. Gradually raise the speed to medium-high and beat until soft peaks form when the beater is raised. Gradually beat in the remaining 1 tablespoon of sugar and continue beating until stiff peaks form when the beater is raised slowly.
Add the Meringue to the Batter Using a large balloon whisk, slotted skimmer, or large silicone spatula, gently fold the meringue into the batter. Scrape the batter into the prepared pan and, using an offset spatula, smooth it as evenly as possible.
Bake the Cake Bake for 7 to 10 minutes, or until golden brown and the cake springs back when pressed lightly in the center. Have ready a small sharp knife.
Unmold and Cool the Cake Run the tip of a sharp knife around the sides to dislodge any cake that may have attached itself to the sides of the pan and unmold the cake at once. Slip a small offset spatula under the narrow edge of the parchment to loosen it. Grasp the parchment and gently slide the cake from the pan onto a baking sheet or inverted sheet pan. Cover with plastic wrap lightly coated with nonstick cooking spray. Cool until it is no longer warm to the touch, about 20 minutes.
Make the Templates Make the templates for cutting the cake into 4 pieces: 1 continuous piece for the bottom and sides, 2 ends, and 1 top. Measure the outside of the pan and transfer the measurements to sheets of paper or card stock. The templates should be slightly oversized to allow for trimming to fit. Cut out the templates.
Chocolate Mousse Filling
Makes 4 cups/29.6 ounces/840 grams
9.5 ounces (270 grams) bittersweet chocolate, 60% to 62% cacao, chopped
2 cups (473 ml, 16.4 ounces, 464 grams) heavy cream
10 (to 14) egg yolks, at room temperature (¾ cup, 177 ml, 6.5 ounces, 186 grams)
1 Tablespoon (15 ml) pure vanilla extract 1 egg white, at room temperature (2 tablespoons, 30 ml, 1 ounce, 30 grams)
1/8 teaspoon cream of tartar
3 Tablespoons superfine sugar 1.3 ounces, 37 grams)
Make the Chocolate Custard Have ready a fine-mesh strainer suspended over a stand mixer bowl and a handheld mixer.
In the top of a double boiler set over hot, not simmering, water (do not let the bottom of the container touch the water), heat the chocolate and cream. Stir often with a silicone spatula until the chocolate is completely melted. Remove it from the heat.
In a medium bowl, lightly whisk the egg yolks. Stir several tablespoons of the hot chocolate mixture into the yolk mixture. Gradually pour the yolk mixture into the remaining chocolate mixture, stirring constantly.
Continue stirring, occasionally scraping the bottom of the container to ensure uniform consistency. Heat the mixture to just before the boiling point (170° to 180°F/77° to 82°C). Steam will begin to appear and the mixture will be slightly thicker than cream. It will leave a well-defined track when a finger is run across the spatula. Immediately remove the container from the heat and pour the mixture through the strainer into the mixer bowl, scraping up the thickened cream that settles on the bottom of the container. Press it through the strainer and stir in the vanilla.
Press a piece of plastic wrap onto the surface of the chocolate custard to prevent a skin from forming. Refrigerate for 2½ to 3 hours, stirring every 20 minutes, until cool to the touch. If you are ready to fill the cake-lined pan sooner, you can speed cooling by setting the bowl in an ice water bath (see page 538) and stirring frequently. Do not let the mixture get too cold or it will be too stiff to incorporate air from the meringue. The ideal temperature is 65° to 68°F/19° to 20°C.
Beat the Egg White into a Stiff Meringue In a medium bowl, beat the egg white and cream of tartar on medium-low speed until foamy. Gradually raise the speed to medium-high and beat until soft peaks form when the beater is raised. Gradually beat in the sugar until stiff peaks form when the beater is raised.
Complete the Chocolate Mousse Filling With the whisk beater, on low speed, beat the chocolate mixture for about 30 seconds, or just until very soft, floppy peaks form when the beater is raised. Gently fold the meringue into the mousse until uniform in color.
Cut the Cake Pieces Invert the cake onto a wire rack and carefully remove the parchment. Reinvert the cake onto the baking sheet or inverted sheet pan and remove the plastic wrap. Place the templates on top of the cake so that they all fit. Use kitchen scissors to cut out the 4 cake pieces.
Line the Pan with the Cake Pieces Line the loaf pan with a sheet of plastic wrap cut 2 feet long, with the excess extending past one end of the pan. Lightly coat the plastic wrap with nonstick cooking spray. Carefully insert the bottom and sides piece of cake into the pan, crust side against the pan. Trim the 2 end pieces to fit tightly against the bottom and sides of the cake.
Compose the Cake Spoon half of the chocolate mousse into the cake-lined pan. With a small metal offset spatula, lightly press the mousse into the pan to ensure that the mousse fills the corners of the cake. Repeat with the rest of the chocolate mousse. If necessary, trim the tops of the cake pieces to be flush with the top of the pan. Place the top cake piece, crust side up, over the mousse filling and trim its edges to fit inside the cake’s side and end pieces.
Fold over the extended plastic wrap to cover the top of the pan. Lightly press down on the cake’s top. Wrap any excess plastic wrap tightly around the sides of the pan. Set a small cutting board or heavy pan large enough to cover the entire top of the loaf pan on top.
Let the cake sit for 3 hours at room temperature for the chocolate mousse to set. The cake cuts best and has the best texture at room temperature.
Unmold the Cake Remove the cutting board and fold back the plastic wrap to uncover the top of the cake. Place a serving plate or the cutting board on top of the pan and invert the cake. Remove the pan. Gently peel off the plastic wrap.
Use a straight-edge knife to slice the cake from top to bottom. Between slices, wipe off the knife to minimize the likelihood of the chocolate mousse spreading onto the cake.
Store Airtight: room temperature, 6 hours; refrigerated, 3 days. Do not freeze, because the texture will become less smooth.
Highlights for Success
The chocolate mixture will continue to thicken after a few minutes at room temperature. The safest way to prevent over beating is to use the stand mixer until the mixture starts to thicken and then continue by hand with a whisk when folding in the meringue.
Excerpted from The Baking Bible, © 2014 by Rose Levy Beranbaum. Reproduced by permission of Houghton Mifflin Harcourt. All rights reserved.
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