Chocolate Hazelnut Layer Cake

I love making birthday cakes. I love birthdays and I love cake. This year, Susan requested a cake with the flavors of chocolate and hazelnut - which just so happens to be my favorite flavor combination lately.

The base of this cake is a hazelnut dacquoise, topped with a crunchy layer of chocolate, rice krispies, and hazelnuts. This is topped with layers of chocolate cake and chocolate mousse. The whole cake is covered with a thin layer of chocolate mousse and then a layer of Nutella chocolate frosting. Finally, crushed hazelnuts adorn the sides of the cake. It's not a quick cake to make, but it's much easier when you spread the work over a few days.

I'm not sure which she liked better - the cake or the birthday dance that Derrick and I did for her - but I'm betting it was the cake.





Chocolate Cake (from Epicurious)

3 ounces fine-quality semisweet chocolate
1 1/2 cups hot brewed coffee (I used hazelnut coffee)
3 cups sugar
2 1/2 cups all-purpose flour
1 1/2 cups unsweetened cocoa powder (not Dutch processed)
2 teaspoons baking soda
3/4 teaspoon baking powder
1 1/4 teaspoons Kosher salt
3 large eggs
3/4 cup vegetable oil
1 1/2 cups well-shaken buttermilk
3/4 teaspoon vanilla extract

Preheat the oven to 300°F and spray 2 9" pans with baking spray (I used 2 9" pans and made an additional 3 inch cake; I've also used just the 2 9" pans before; 2 10" pans also work). Line bottoms with rounds of parchment paper and spray paper as well.

Finely chop the chocolate and place in a medium bowl; pour hot coffee over the chocolate. Let stand for one minute, then stir until chocolate is melted and the mixture is smooth.

Sift together the sugar, flour, cocoa powder, baking soda, baking powder, and salt in a large bowl.

In another large bowl, with an electric mixer, beat eggs until thickened slightly and lemon colored (about 3 minutes with a standing mixer or 5 minutes with a hand-held mixer).

Slowly add oil, buttermilk, vanilla, and melted chocolate mixture to eggs, beating until combined well.

Add sugar mixture and beat on medium speed until just combined well.

Divide batter between pans and bake in the middle of oven until a tester inserted in center comes out clean, 1 hour to 1 hour and 10 minutes.

Cool the cake layers completely in pans on racks. Run a thin knife around edges of pans and invert layers onto racks. Carefully remove parchment paper and cool layers completely.

Note: You only need one cake layer for this recipe, so either half the recipe or freeze the unused layer for up to 2 months.


Hazelnut Dacquoise (adapted from Pierre Herme)

2/3 cup finely ground hazelnut flour*
1 cup powdered sugar
3 large egg whites, room temperature
2 1/2 tablespoons sugar
1/2 to 1 cup toasted, skinned hazelnuts, coarsely chopped

Preheat the oven to 325°F. Line a 9" springform pan with parchment paper.

*If you are making your own hazelnut flour, toast the hazelnuts in a single layer on a baking sheet in a 350°F oven for 10-15 minutes until golden and aromatic. Remove from oven, wrap in towel, and let steam for 1 minute. Rub the nuts together vigorously (still in the towel) to loosen skins. This is messy! Most of the skins will have fallen off (it's ok to leave some on); pick out the hazelnuts and coarsely grind in food processor. I sometimes buy hazelnut flour, as the difference in taste is minimal. It is still necessary, however, to put it through the food processor with the powdered sugar to make it fine enough, especially if you're using it for something like macarons. Otherwise the small pieces of nuts will get stuck in your piping tip.

Place the hazelnut flour and powdered sugar in the food processor, and pulse a few times to combine.

Separate the eggs (Use a warm water bath to first bring the eggs to room temperature if you forget to take them out of the fridge soon enough). You can store the yolks in the fridge for a day or two for another recipe (ice cream, sweet tart dough, pastry cream, yellow butter cake, or lemon curd perhaps). You may want to add just a bit of water to the yolks for storage.

Whip the egg whites just until they turn opaque.

Gradually add the sugar, and beat to firm, glossy peaks.

Gently fold the nut mixture into the whites with a flexible rubber spatula. Pour the mixture into the springform pan and use the spatula to make it as even as possible.

Scatter the chopped hazelnuts over the top, and lightly press into batter. I've done this dacquoise with and without the chopped hazelnuts on top.

Bake for 25 to 30 minutes, until golden brown and firm. Cool completely on a rack. The dacquoise can be up to 2 days ahead (wrapped airtight and kept at room temperature) or frozen for up to a month.


Chocolate Hazelnut Crisp Layer

3.5 ounces bittersweet chocolate/hazelnut bar
3.5 ounces milk chocolate/hazelnut bar
2 cups rice krispies

Melt chocolate bars; stir in rice krispies. Spread over dacquoise layer.

Chill for at least 30 minutes. Remove the sides of the pan, and carefully peel off parchment layer.

This amount yields a relatively thick crunch layer. Use 1/2 to 3/4 of the recipe for a thinner layer. Feel free to use pure chocolate rather than the chocolate/nut bars, or stir in your own chopped hazelnuts into the melted chocolate.

Chocolate Mousse (adapted from Epicurious)

4 ounces semi-sweet chocolate
2 ounces milk chocolate
1 teaspoon vanilla extract
1 pinch of Kosher salt
1 1/2 cups chilled heavy cream, separated
1/8 cup sugar

Combine chocolate, vanilla and salt in bowl.

Bring 1/2 cup cream to boil in heavy small saucepan; pour over chocolate. Let sit for one minute, then stir until smooth. Cool to room temperature, stirring occasionally.

Beat 1 cup cream and sugar in large bowl to stiff peaks. Fold into chocolate mixture.

Chill until spreadable, about 2 hours.

Chocolate-Nutella Frosting (adapted from Chocolate Chocolate)

6 tablespoons unsalted butter
3 ounces unsweetened chocolate, melted and cooled to tepid
1/3 to 1/2 cup Nutella, depending on taste (taste is somewhat subtle with 1/3 cup)
Large pinch of Kosher salt
1 tablespoon vanilla extract
5-6 cups powdered sugar, sifted
2/3 cup milk, heated to tepid

Beat butter on medium speed for 1-2 minutes.

Blend in the melted chocolate, Nutella, salt, vanilla, 1/3 cup milk, and 2 1/2 cups powdered sugar.

Add in the rest of the milk; beat for 1 minute.

Add the rest of the powdered sugar; beat for 1 minute. Use more powdered sugar for a stiffer consistency, less for a softer consistency.

Refrigerate the frosting for 1-2 hours until spreadable.

You will have some extra frosting.



To Assemble:


Place dacquoise on a cake plate or cake round.

Cut one of the cake layers in half, horizontally. Carefully place one half on top of the dacquoise.

Spread a light layer of mousse on top.

Place the next cake layer on top of the mousse.

Spread the remaining mousse over the top and sides of the cake.

Chill for at least 30 minutes. The mousse needs to be hard enough to spread the frosting over.

Frost the cake. You will likely have frosting left over.

While frosting is still soft, cover the sides of the cake with chopped hazelnuts (I used about 1/2 cup). Refrigerate cake to set. Remove from fridge 2 hours before serving.


The birthday girl thought the cake was even better the next day, after the flavors had had a chance to meld.

Tips: This is a time-intensive cake, but you can break up the work over several days. I made the cake layers on Tuesday night and froze them and the dacquoise on Wednesday night. On Friday, I made the mousse, and assembled the cake up to the mousse. On Saturday morning I made the frosting, and I frosted the cake a few hours later. It was served Saturday night. You may also wish to make a slightly easier version of the cake, below.

Variations:

For a slightly less complicated recipe, use only the chocolate mousse or chocolate Nutella frosting for both filling and frosting the cake. You will need to make 1 1/2 to 2 recipes of the mousse if you use only mousse and 1 1/2 recipes of the frosting if you use only frosting.


Thank you Derrick for taking some of the photos!