The Scotchmallow Cake
My daughter Sophia never met a chocolate cake she didn’t fall madly in love with, so a special occasion like her thirteenth birthday demanded a real showstopper. This extravagant confection features rich chocolate cake, gooey caramel, and a pillowy layer of homemade marshmallow. A mousse-like buttercream and real Belgian chocolate sprinkles push this cake over the top. Save time (and your sanity) by preparing the marshmallow layer up to one week in advance.
SERVES 8 TO 10
21/2 cups [350 g] all-purpose flour
2 tsp baking powder
1/2 tsp baking soda
3/4 tsp fine sea salt
2/3 cup [50 g] Dutch-process cocoa powder
1 tsp instant espresso powder
3 oz [85 g] semisweet chocolate, finely chopped
1 cup [240 ml] boiling water
2 tsp vanilla extract
1 cup [240 ml] buttermilk
1/2 cup [110 g] unsalted butter, at room temperature
1/2 cup [120 ml] canola or vegetable oil
11/2 cups [300 g] granulated sugar
1 cup [200 g] firmly packed dark brown sugar
3 eggs, plus 2 egg yolks, at room temperature
CHOCOLATE SILK BUTTERCREAM
11/2 cups [300 g] granulated sugar
1 tsp vanilla extract
1/8 tsp fine sea salt
3 cups [660 g] unsalted butter, at room temperature
12 oz [340 g] semisweet chocolate (56 to
60 percent cacao), melted and cooled
1 cup [200 g] granulated sugar
2 Tbsp water
3/4 cup [180 ml] heavy cream
1 tsp vanilla extract
1/4 tsp fine sea salt
Cornstarch for dusting
1 cup [240 ml] cold water
3 Tbsp unflavored granulated gelatin
2 cups [400 g] granulated sugar
3/4 cup [180 ml] light corn syrup
1/4 tsp fine sea salt
11/2 tsp vanilla extract
Confectioners’ sugar for dusting
1 cup [180 g] Belgian chocolate sprinkles.
Position a rack in the center of the oven. Preheat the oven to 350°F [180°C]. Coat two 9-in [23-cm] round cake pans with nonstick cooking spray. Line the bottoms with parchment paper.
In a medium bowl, sift together the flour, baking powder, baking soda, and salt. Set aside.
In a heatproof bowl, combine the cocoa powder, espresso powder, and chocolate. Pour in the boiling water and stir until the chocolate is melted and the mixture is smooth. Stir in the vanilla and buttermilk. Set aside and let cool.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter and oil on medium speed until creamy. Add both the sugars and continue beating until light and fluffy, 3 to 4 minutes. Add the eggs, one at a time, beating well after each addition. Beat in the egg yolks. Scrape down the sides of the bowl.
Add one-third of the dry ingredients to the batter and beat at low speed for 10 to 15 seconds, just until combined. Beat in half of the chocolate mixture for a few seconds, just to combine. Beat in another one-third of the dry ingredients, followed by the remaining chocolate mixture. Scrape down the sides of the bowl, and finally beat in the remaining one-third of the dry ingredients at low speed just until no streaks of flour remain, about 10 to 15 seconds. Divide the batter evenly between the prepared pans and spread the tops smooth with a spatula.
Bake for 25 to 30 minutes, until a wooden skewer inserted into the center of each cake comes out clean. Transfer the pans to wire racks and let cool for 10 minutes. Invert the cakes onto the racks, discard the parchment paper, and let cool completely.
To make the buttercream:
Fill a large sauté pan with water and bring to a simmer over medium heat. Combine the eggs and sugar in the bowl of a stand mixer. Set the bowl in the pan of simmering water. By hand, using a large balloon whisk, vigorously beat the eggs and sugar until the sugar is completely dissolved and the mixture is thick, fluffy, and very hot, 3 to 4 minutes. Use an instant-read candy thermometer to check the temperature of the whipped eggs and sugar; it should register between 120° and 140°F [48° and 60°C].
Remove the bowl from the hot water and return to the stand mixer. Using the whisk attachment, beat the eggs at high speed until they are tripled in volume, form stiff peaks, and the bottom of the bowl is completely cool to the touch, 10 to 13 minutes. Beat in the vanilla and salt.
With the mixer still on high speed, add the softened butter, 2 Tbsp at a time, adding more butter only as each addition is fully incorporated. Don’t panic if the buttercream looks too liquid or starts to curdle as you add the butter. It will magically emulsify into a smooth, creamy frosting by the time the last bit of butter is beaten in. Hold your breath and keep beating. When the buttercream is smooth and all the butter has been incorporated, turn off the mixer and, using a rubber or silicone spatula, carefully fold in the cooled melted chocolate by hand.
To make the caramel drizzle:
In a large, heavy saucepan over medium-high heat, combine the sugar and water. Cook, without stirring but swirling the pan occasionally, until the sugar is completely dissolved. Bring to a boil and cook, undisturbed, until the syrup turns a deep amber (the color of an old penny), 4 to 6 minutes. Immediately remove the pan from the heat and, using a long-handled wooden spoon, stir in the cream. Be careful, as the cream will bubble vigorously when it hits the hot caramel. Return the pan to medium-low heat and stir the sauce until it is thick and creamy, 2 to 3 minutes. Remove from the heat, stir in the vanilla and salt, and let cool.
To make the marshmallow layer:
At least 1 day (and up to 1 week) ahead, coat a 9-in [23-cm] round cake pan with nonstick cooking spray and dust liberally with cornstarch. Set aside.
Pour 1/2 cup [120 ml] of the cold water into the bowl of a stand mixer and sprinkle with the gelatin. Allow the gelatin to absorb the water, 15 to 20 minutes.
In a large saucepan over medium heat, combine the remaining 1/2 cup [120 ml] water, the granulated sugar, corn syrup, and salt. Heat, swirling the pan occasionally, until the sugar dissolves. Increase the heat to high and let the syrup come to a boil. Cook, without stirring, until it reaches 240°F [115°C] on an instant-read candy thermometer. Do not allow the syrup to go past 244°F [117°C] or the marshmallow will be tough and rubbery
With the mixer on low, beat the syrup into the gelatin, using the whisk attachment of the mixer. Increase the mixer speed to high and continue beating until the marshmallow is thick, fluffy, and very white but still warm, 10 to 13 minutes. Beat in the vanilla.
Scrape the marshmallow into the prepared pan, smooth the surface with a spatula, and dust with confectioners’ sugar. Let the marshmallow stand, uncovered, for 8 to 12 hours to firm up. Turn the marshmallow onto a piece of parchment paper lightly dusted with confectioners’ sugar. Brush away any excess cornstarch. (Store the marshmallow layer in a covered container or large, self-sealing plastic bag for up to 1 week.)
To finish the cake:
Place one cake layer, bottom-side up, on a cardboard cake round. Transfer 1 rounded cup [about 300 g] buttercream into a disposable piping bag fitted with a large round or star tip and set aside.
Spread the surface of the cake with 1 rounded cup buttercream. Drizzle with approximately 1/3 cup [80 ml] of the cool caramel drizzle. Top with the second layer of cake. Spread with another 1 cup of buttercream and drizzle with another 1/3 cup of the caramel.
Use a pastry brush to brush any remnants of cornstarch and confectioners’ sugar from the marshmallow layer and place it on top of the cake. Press down gently to make sure it has adhered to the caramel and buttercream. Frost the sides of the cake with a thin coat of buttercream to form a crumb coat (see page 21), and refrigerate for 15 to 20 minutes to firm up. With the remaining buttercream, frost the top and sides of the cake, completely covering the cake and marshmallow. If desired, press Belgian chocolate sprinkles on the sides of the cake (place the cake and turntable, if using, on a rimmed baking sheet to catch any errant sprinkles). Press the sprinkles by the handful around the sides of the cake, slowly spinning the turntable as you go (if you’re using a turntable) until the cake is completely encrusted.
Spoon approximately 1/2 cup [120 ml] of the lukewarm caramel over the top of the cake, letting it drizzle down the sides. With the reserved buttercream, pipe a decorative pattern over the top of the cake. Serve at room temperature.
Refrigerate in a cake carrier for up to 2 days. Let the cake come to room temperature for 1 to 2 hours before serving.