Active Time

　　1½ hours

　　Total Time

　　2 hours

　　This coffee and walnut cake is inspired by the classic British dessert, though I’ve skipped the standard American buttercream and instead gone extra-silky with Swiss meringue buttercream that’s laced with a touch of cocoa powder. (Not sure about the difference? Jump to this guide to types of frosting.) The cake layers, flavored with finely ground toasted walnuts, are surprisingly sponge-like and light. The walnuts and the coffee, in the form of instant espresso powder, give a pleasantly bitter edge to this otherwise rich and sweet cake.

　　This recipe makes a generous batch of mocha buttercream to allow for the most ornate of decorations; any leftovers can be frozen in an airtight container for up to three months. (Bring to room temperature and beat again before using.) If the buttercream ever looks split while you’re making it, with fat separating from the meringue, keep beating on high speed and it will smooth out soon enough. If it stiffens to the point that the butter will not incorporate, place the bowl back over the simmering water for a few seconds to let the mixture reheat, then continue beating as before, adding the remaining butter a tablespoon at a time.

　　For those who would like to lean into the deeper tannic notes of the walnuts and coffee, heat ¼ cup sugar and 3 Tbsp. water in a small saucepan, stirring until the sugar dissolves. Stir in 1 Tbsp. amaro and ½ tsp. instant espresso powder. Dab syrup on the cut layers of the cake with a pastry brush before frosting.

　　

Ingredients

Makes one 8"-diameter cake

　　

Cake

¾ cup (1½ sticks) unsalted butter, plus more for pans

　　2 cups (250 g) raw walnuts

　　½ cup plus 2 Tbsp. vegetable oil or refined coconut oil, melted

　　2 cups (250 g) all-purpose flour

　　2¼ tsp. baking powder

　　1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt

　　½ tsp. baking soda

　　4 large eggs

　　1¼ cups (250 g) sugar

　　2 tsp. vanilla extract

　　1 tsp. instant espresso powder

　　2 Tbsp. whole milk

　　

Buttercream and assembly

8 large egg whites

　　2¼ cups (450 g) sugar

　　¾ tsp. Diamond Crystal or ½ tsp. Morton kosher salt

　　¼ tsp. cream of tartar

　　1 tsp. vanilla extract

　　3 cups (6 sticks) unsalted butter, room temperature, cut into pieces

　　¼ cup (21 g) unsweetened cocoa powder, sifted if needed

　　2 tsp. instant espresso powder

　　

Cake

Step 1

Place a rack in middle of oven; preheat to 325°. Lightly butter three 8"-diameter cake pans and line bottoms with parchment paper rounds. Toast 2 cups (250 g) raw walnuts in a single layer on a rimmed baking sheet, tossing halfway through, until golden brown, 12–14 minutes. Let cool. Set aside 1 cup walnuts for serving.

　　

Step 2

Meanwhile, cook ¾ cup (1½ sticks) unsalted butter in a small saucepan over medium heat, stirring often, until it foams, then browns, 6–8 minutes. Remove from heat and immediately stir in ½ cup plus 2 Tbsp. vegetable oil or refined coconut oil, melted. Set brown butter mixture aside.

　　

Step 3

Pulse remaining 1 cup toasted walnuts in a food processor until coarsely ground (it should be the texture of panko). Transfer to a large bowl and whisk in 2 cups (250 g) all-purpose flour, 2¼ tsp. baking powder, 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt, and ½ tsp. baking soda.

　　

Step 4

Process 4 large eggs, 1¼ cups (250 g) sugar, 2 tsp. vanilla extract, and 1 tsp. instant espresso powder in food processor (no need to clean bowl) until mixture is lightened in color and thickened, about 30 seconds. Stir 2 Tbsp. whole milk into reserved brown butter mixture. With motor running, gradually stream brown butter mixture into egg mixture and process until combined. Add dry ingredients and process just until a smooth batter forms. Divide batter among prepared pans.

　　

Step 5

Bake cakes, rotating pans front to back after 15 minutes, until puffed and just starting to pull away from the sides of pans and a tester inserted in the centers comes out clean, 20–22 minutes. Transfer pans to wire racks and let cakes cool 15 minutes. Run a small knife around edges of each cake to release from pan if needed. Turn out cakes onto racks and remove parchment paper; discard. Turn cakes right side up and let cool completely.

　　

Buttercream and assembly

Step 6

Combine 8 large egg whites, 2¼ cups (450 g) sugar, ¾ tsp. Diamond Crystal or ½ tsp. Morton kosher salt, and ¼ tsp. cream of tartar in the bowl of a stand mixer. Set over a medium saucepan filled with 1½" of simmering water (bowl should not touch water). Heat, stirring and scraping often with a heatproof rubber spatula, until sugar is dissolved and an instant-read thermometer registers 185°, 10–15 minutes.

　　

Step 7

Fit bowl onto stand mixer fitted with whisk attachment and beat, starting on low speed and gradually increasing to high, until meringue is shiny and stiff, 8–10 minutes. Beat in 1 tsp. vanilla extract.

　　

Step 8

With mixer on medium speed, add 3 cups (6 sticks) unsalted butter, room temperature, cut into pieces, a piece at a time, mixing until incorporated before adding more. Once all the butter has been added, increase speed to high and beat 1 minute. Transfer buttercream in bowl to refrigerator and chill 30 minutes.

　　

Step 9

Fit bowl with buttercream back onto stand mixer and add ¼ cup (21 g) unsweetened cocoa powder, sifted if needed, and 2 tsp. instant espresso powder. Beat on medium-low speed, scraping down sides as needed, until combined.

　　

Step 10

Using a large serrated knife and long sawing strokes, remove tops of cakes to level if needed. Place a cake layer, right side up, on a cake stand or large plate. Using an offset spatula, spread ¼ cup buttercream over cake, working all the way to the edges. Place second cake layer, right side up, on top; spread another ¼ cup buttercream over cake, working all the way to the edges. Place third cake layer, cut side down, on top, and press lightly to adhere. Spread top and sides of cake with ½ cup buttercream in a thin, even layer. Chill, uncovered, at least 1 hour and up to 12 hours. (If chilling cake longer than 1 hour, cover remaining buttercream in bowl and chill. Bring to room temperature and beat again before using.)