Twelve Layered Mocha Cake
For cake layers
4 large egg yolks at room temperature 30 minutes
2 tablespoons whole milk
1/2 teaspoon pure vanilla extract
3/4 cup sugar, divided
1/2 cup all-purpose flour
1/4 teaspoon salt
2 large egg whites at room temperature 30 minutes
For soufflé layers
6 oz fine-quality 60%-cacao bittersweet chocolate, finely chopped
1/4 cup water
5 large eggs, separated, at room temperature 30 minutes
1/4 teaspoon salt
1/2 cup sugar, divided
1 tablespoon unsweetened cocoa powder
For meringue layers
2/3 cup hazelnuts (3 1/2 oz)
3 large egg whites at room temperature 30 minutes
1/8 teaspoon salt
1/8 teaspoon cream of tartar
1/2 cup sugar
1/3 cup water
2 tablespoons sugar
1 teaspoon instant-espresso powder
Coffee and mocha and buttercreams
Equipment:3 (15-by 10-inch) 4-sided sheet pans (1/2 inch deep)
Make cake layers:
Preheat oven to 350°F with rack in middle. Butter 1 sheet pan and line
bottom with parchment paper, then butter parchment. Dust with flour,
knocking out excess.
Whisk together yolks, milk, vanilla, and 1/2 cup sugar in a large bowl until
combined well, then whisk in flour and salt until smooth. (Batter will be
Beat whites with an electric mixer until they just hold soft peaks. Beat in
remaining 1/4 cup sugar, 1 Tbsp at a time, and beat until whites just hold
Fold one third of whites into batter to lighten, then fold in remainder
gently but thoroughly.
Spread batter evenly in pan and rap against counter to release any air
bubbles. Bake until cake is dry to the touch and pale golden, 10 to 11
minutes. (Leave oven on.) Cool completely in pan on a rack. Halve cake
crosswise, cutting through parchment, to form 2 (10-by 7 1/2-inch) layers.
Prepare soufflé layers while cake bakes:
Line second sheet pan with parchment paper. Melt chocolate with water (See Tips), then cool to lukewarm. Beat yolks, salt, and 1/4 cup sugar in a large bowl with an electric mixer at high speed until thick and pale, about 5
minutes with a stand mixer or 8 minutes with a handheld. Fold in melted
chocolate. Beat whites with cleaned beaters until they hold soft peaks. Beat
in remaining 1/4 cup sugar, 1 Tbsp at a time, and beat until whites just
hold stiff peaks, about 5 minutes. Fold one third of whites into chocolate
mixture to lighten, then fold in remainder gently but thoroughly. Spread
batter evenly in lined sheet pan.
Bake soufflé layers: Bake until puffed and a wooden pick inserted into
center comes out with a few crumbs adhering, 25 to 30 minutes. Transfer pan to a rack, then cover top of soufflé with 2 layers of damp paper towels. Let stand 5 minutes. Remove towels and cool soufflé completely in pan (soufflé will deflate as it cools). Sift cocoa over soufflé, then loosen edges with a sharp knife. Halve soufflé crosswise, cutting through parchment, to form 2 (10-by 7 1/2-inch) layers.
Make meringue layers: Toast hazelnuts (See Tips), then cool, wrapped in a
kitchen towel, and rub off any loose skins. Reduce oven to 250°F. Finely
Beat whites with salt and cream of tartar using electric mixer until they
just hold soft peaks. Beat in sugar, 1 tablespoon at a time, and beat until
meringue is stiff but still glossy. Line bottom of third sheet pan with
parchment. Put small dabs of meringue under corners of parchment to secure
to baking sheets. Fold nuts into meringue and spread evenly in pan. Bake
until set and pale golden, 25 to 30 minutes. Halve meringue crosswise,
cutting through parchment, to form 2 (10-by 7 1/2-inch) layers. Return to
oven and bake until crisp, 45 minutes to 1 hour more. Cool in pan, then peel
Make syrup and assemble cake: Bring water, sugar, and espresso powder to a boil, stirring until sugar has dissolved. Cool. Loosen edges of 1 cake layer
with a knife and invert onto a flat platter. Carefully peel parchment from
cake and brush with some of syrup. Spread with 1 1/4 cups mocha buttercream.
Top with 1 meringue layer and spread with 1 1/4 cups coffee buttercream.
Carefully invert 1 soufflé layer onto buttercream and peel off parchment,
then gently spread with 1 1/4 cups coffee buttercream. Repeat layering,
ending with coffee buttercream (there will be some left over). Chill at
least 1 hour (after that, wrap in plastic wrap). Trim all around cake with a
long sharp knife to neaten edges. Bring to room temperature (about 1 hour)
Cooks’ notes: Cake, soufflé, and meringue layers can be baked 1 day ahead
of assembly and kept, wrapped in plastic wrap, at room temperature.
Assembled cake can be chilled up to 2 days.