Outrageously Good Chocolate Layer Cake
introduction
What makes a chocolate layer cake great? Intense, true chocolate flavor and a fine, moist, structured crumb. Four cake layers and real chocolate buttercream never hurt. We did have to jockey ingredients around considerably—adding here, dumping there—to groom this cake to perfection. Melted bittersweet chocolate and whole milk—two ingredients you’d think chocolate cake batter might appreciate—made the crumb leaden and the flavor weak. Getting milk out of the way also left ample room for butter, whose flavor contribution is always unsurpassed, while a measure of almond oil conferred moistness and the experience of an enhanced chocolate crumb. Anson Mills cake flour nearly scored an exclusive in this recipe, but in the end, the cake’s crumb and structure were best—neither stodgy, fudgy, nor fairy-dust light—with an even ratio of cake and pastry flours.
The buttercream for this cake, a collaboration between custard and meringue involving two processes and two different parts of the egg, delivers performance, stability, and texture unsurpassed by other buttercreams—Swiss, French, Italian, or German. It is both silken and creamy, not slippery, surprisingly resilient, and, with the addition of melted bittersweet chocolate, the best buttercream we know. We owe a debt of gratitude to Rose Levy Beranbaum for this formula, which has a Gaston Lenôtre pedigree, and is the same buttercream Kay produced regularly at Lenôtre in Berlin.
Baking Notes
Use boiling water or hot coffee in the cake, whichever you prefer. We were divided in our preference—some tasters appreciated the purity of chocolate flavor in a cake make with water, while others liked the subtly bitter and roasted notes of brewed coffee.
To get the perfect chocolate flavor balance in the buttercream, it is essential to use bittersweet chocolate containing about 80 percent cocoa solids. Just as important is selecting a chocolate whose palate impact is not noticeably acidic, otherwise the acidity will register as harsh and oddly tangy in the finished buttercream.
equipment mise en place
To make the cake, you will need a digital kitchen scale, small bowl, a whisk, two 9-inch round cake pans, parchment paper rounds that fit into the pans, a stand mixer fitted with the flat-beater attachment, a 1-quart liquid measuring cup or medium bowl, a silicone spatula, two wire racks, and a paring knife.
To make the buttercream, you will need a fine-mesh strainer, two small bowls, a whisk, a heavy-bottomed small saucepan, a digital instant-read thermometer, a medium saucepan, a medium heatproof bowl, a silicone spatula, a spotlessly clean large bowl, a handheld mixer, and a stand mixer fitted with the flat-beater attachment.
To assemble the cake, you will need a serrated knife, a 9-inch cardboard cake round, and an offset icing spatula.
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for the cake:
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3ounces unsweetened Dutch-processed cocoa powder
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9ounces boiling water or hot brewed coffee
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8ounces unsalted European-style butter, cut into 8 pieces, room temperature, plus additional for greasing the pans
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5ounces Anson Mills Colonial-Style Fine Cloth-Bolted Pastry Flour, plus additional for dusting the pans
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5
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1tablespoon baking powder
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1¼teaspoons fine sea salt
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13ounces sugar
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6.8ounces shelled eggs (about 4 large), room temperature
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2ounces almond oil
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2teaspoons vanilla extract
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for the buttercream:
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3.5ounces egg yolks (from 5 or 6 large eggs)
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3.5ounces plus 3.5 ounces sugar
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4ounces whole milk
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1teaspoon vanilla extract
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¼teaspoon fine sea salt
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8ounces good-quality bittersweet chocolate (about 80 percent cocoa solids), chopped
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1ounce water
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2ounces egg whites (from 2 large eggs)
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⅛teaspoon cream of tartar
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1pound unsalted European-style butter, room temperature
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Make the cake: Adjust an oven rack to the lower-middle position and heat the oven to 350 degrees. Place the cocoa in a small bowl and pour the boiling water or hot coffee over it. Whisk until completely smooth, then let cool to room temperature.
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Meanwhile, butter two 9-inch round cake pans, line the bottoms with parchment-paper rounds, and butter the parchment. Sprinkle the pans with flour, tilting them to coat the bottom and sides, then knock out the excess. Into the bowl of a stand mixer, sift the pastry flour, cake flour, baking powder, and salt. Add the sugar, whisk to combine, and set aside.
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When the cocoa mixture is cooled, in a 1-quart liquid measuring cup or medium bowl, whisk together the eggs, almond oil, and vanilla. Add approximately one-third of the cocoa mixture and whisk until homogenous.
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Add the butter and the remaining cocoa mixture to the dry ingredients in the mixer bowl, then attach the bowl to the mixer. Using the flat-beater attachment, mix on low speed until the mixture is evenly moistened, about 1 minute, scraping down the bowl once or twice with a silicone spatula. Increase the speed to medium and beat for about 1½ minutes to build structure in the batter. Scrape down the bowl. With the mixer running on medium-low speed, stream in about one-third of the egg-cocoa mixture and mix until it has been mostly incorporated, then continue to beat for about 30 seconds; scrape down the bowl. Add the remaining egg-cocoa mixture in the same way, in two more batches. Detach the bowl from the mixer and give the batter several folds with the spatula to ensure that it is well combined.
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Divide the batter evenly between the prepared pans, then spread into an even layer and smooth the surface. Bake until the cakes are slightly domed and a toothpick inserted into the centers comes out clean, about 30 minutes. Let the cakes cool in the pans on a wire rack for 10 minutes; the domes should level off. Run a paring knife around the edges. Invert each cake onto a wire rack, lift off the pan, and peel off and discard the parchment. Let the cakes cool completely, at least 1½ hours.
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While the cakes cool, make the buttercream: Set a fine-mesh strainer over a small bowl. In another small bowl, whisk together the egg yolks and 3.5 ounces of the sugar until well combined. In a heavy-bottomed small saucepan, bring the milk to a bare simmer over medium heat. Gradually whisk the hot milk into the yolk mixture, then return the milk-yolk mixture to the saucepan. Cook over medium heat, stirring constantly, until the custard thickens enough to heavily coat the back of a spoon and reaches 175 to 180 degrees on a digital instant-read thermometer; do not let it reach a simmer. Immediately pour the custard into the strainer. Stir the vanilla and salt into the custard, then let cool to room temperature; occasional stirring will help it cool more quickly.
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While the custard cools, fill a medium saucepan with about an inch of water and bring to the barest simmer over medium heat. Place the chocolate in a medium heatproof bowl and set the bowl on the saucepan. Melt the chocolate, stirring occasionally with a silicone spatula, until completely melted and smooth. Remove the bowl from the saucepan and let the chocolate cool to room temperature, stirring occasionally.
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When both the custard and chocolate are cooled, in a heavy-bottomed small saucepan, combine the remaining 3.5 ounces sugar and the water; set the pan aside. Place the egg whites in a spotlessly clean large bowl and beat with a handheld mixer on medium-low speed until frothy, about 15 seconds. Add the cream of tartar. At this point, set the saucepan over medium heat and bring the sugar mixture to a simmer, occasionally swirling the pan to help dissolve the sugar. As soon as the syrup reaches a simmer, begin beating the egg whites on medium-high speed and continue to beat until the whites hold soft peaks, no longer. When the sugar syrup registers 245 to 248 degrees, begin to drizzle it into the egg whites as you beat them on medium-high speed, making sure to move the beaters to the areas where the syrup lands. After all the syrup has been added, continue to beat the meringue on medium-high speed until it is glossy, voluminous, and holds soft peaks, about 5 minutes; do not overbeat.
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In the bowl of a stand mixer fitted with the flat-beater attachment, beat the butter on medium speed until soft and creamy, 30 to 45 seconds. With the mixer running, slowly pour in the cooled custard and beat until fully incorporated. Scrape down the bowl. With the mixer running on medium speed, add the meringue one heaping spoonful at a time, then beat until homogenous. Scrape down the bowl. With the mixer now running on medium-low speed, slowly pour in the cooled, melted chocolate, then beat until fully combined. Detach the bowl from the mixer and fold with the spatula, scraping along the bottom and sides of the bowl, until the buttercream is uniformly colored.
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Assemble the cake: Using a serrated knife, cut each cake in half horizontally, creating a total of four layers. Place a small dab of buttercream on the center of a 9-inch cardboard cake round, then place one of the cake layers crust side down on the cake round. Using an offset icing spatula, evenly spread a heaping ½ cup of buttercream onto the cake layer. Place a second cake layer on top and gently press it down. Spread on a layer of buttercream as you did before. Repeat to build the third layer of cake and buttercream. Place the fourth and final cake layer crust side up on top and gently press down. Now cover the sides and top of the cake with a thin coating of buttercream; this is the “crumb coat” that seals in loose crumbs and prevents them from marring the final coating of buttercream. Refrigerate the cake uncovered for 15 to 20 minutes to set the crumb coat. Frost the bottom and sides of the cake with a thick layer of the remaining buttercream, then use the back of a spoon to create swoops and swooshes in the frosting.