Ingredients
Scale
Chocolate Cake
- 2½ cups (300 g) all-purpose flour
- 2 cups (400 g) granulated sugar
- ¾ cup (64 g) unsweetened cocoa powder
- 2 teaspoons baking soda
- 1 teaspoon baking powder
- ½ teaspoon fine salt
- 3 large eggs, room temperature
- 1 cup (240 ml) buttermilk, room temperature
- ½ cup (120 ml) neutral vegetable oil
- 2 teaspoons vanilla extract
- 1 cup (240 ml) hot brewed coffee
Chocolate-Hazelnut Filling and Frosting
- 1½ cups (340 g) unsalted butter, softened
- 5 cups (600 g) powdered sugar, sifted
- ½ cup (43 g) unsweetened cocoa powder, sifted
- ¾ cup (225 g) chocolate-hazelnut spread
- ⅓–½ cup (80–120 ml) heavy cream
- 2 teaspoons vanilla extract
- Pinch of fine salt
Chocolate Ganache
- 8 oz (227 g) semisweet chocolate, finely chopped
- ¾ cup (180 ml) heavy cream
Hazelnut Crunch and Decoration
- ½–¾ cup toasted hazelnuts, roughly chopped
- Chocolate wafer sticks
- Chocolate-hazelnut truffles
- Chocolate-covered wafer pieces
- Chocolate discs
- Dark chocolate pieces
- Milk chocolate pieces
Instructions
- Preheat the oven to 350°F (175°C). Lightly grease three 8-inch square cake pans. Line the bottoms with parchment paper and grease the parchment.
- Add the flour, sugar, cocoa powder, baking soda, baking powder, and salt to a large bowl. Whisk until evenly combined and no large cocoa lumps remain.
- In another bowl, whisk the eggs, buttermilk, vegetable oil, and vanilla. Pour the wet ingredients into the dry ingredients. Mix just until mostly combined.
- Slowly pour in the hot coffee while mixing on low speed. The batter will be fairly thin. Do not add extra flour to thicken it.
- Divide the batter equally between the three prepared pans. For the most even layers, weigh the batter and divide it into three equal portions.
- Bake for 25–30 minutes. Start checking at 25 minutes. A toothpick inserted near the center should come out clean or with a few moist crumbs.
- Cool in the pans for about 10 minutes. Turn the cakes onto wire racks, remove the parchment, and allow them to cool completely before frosting.
- While the oven is still at 350°F, spread the hazelnuts on a baking sheet. Toast for about 8–10 minutes, watching carefully. Cool completely before roughly chopping.
- For the frosting, beat the softened butter for 3–4 minutes until pale and fluffy. Gradually beat in the powdered sugar and cocoa powder.
- Add the chocolate-hazelnut spread, vanilla, and salt. Beat until combined. Start with ⅓ cup heavy cream. Add more cream one tablespoon at a time if needed. The frosting should spread easily but remain firm enough to support the layers.
- Place the first cake layer on a sturdy cake board. Spread an even layer of frosting over it. Sprinkle lightly with toasted chopped hazelnuts.
- Add the second layer. Repeat with frosting and hazelnuts. Position the final cake layer on top.
- Cover the cake with a thin crumb coat. Refrigerate for 20–30 minutes, until the frosting feels firm.
- Apply the remaining chocolate-hazelnut frosting. Smooth the four sides and top with an offset spatula and metal cake scraper. Work carefully around the corners to create the tall square finish.
- Refrigerate the frosted cake for another 20 minutes before adding the ganache.
- Put the finely chopped semisweet chocolate in a heatproof bowl. Heat the heavy cream until steaming and just beginning to simmer.
- Pour the hot cream over the chocolate. Leave untouched for 2 minutes. Stir slowly from the center outward until completely smooth and glossy.
- Allow the ganache to cool until fluid but no longer hot. Test one drip on the back of the chilled cake. If it runs straight to the bottom, let the ganache cool longer.
- Create individual ganache drips around the cake. Spread a thin layer of ganache across the top.
- Pipe chocolate frosting swirls over the top. Decorate with wafer sticks, chocolate-hazelnut truffles, wafer pieces, chocolate discs, dark and milk chocolate pieces, and toasted hazelnuts.
- Add the crispy wafer decorations as close to serving as practical so they remain crunchy.
Notes
- Do not frost warm cake layers.
- Room-temperature eggs and buttermilk mix more evenly into the batter.
- Hot coffee deepens the cocoa flavor. Hot water can be substituted if needed.
- The cake batter is supposed to be relatively thin.
- Toasting the hazelnuts gives the filling a much stronger crunch and nutty flavor.
- Cool toasted hazelnuts completely before putting them onto buttercream.
- Do not make the filling excessively thick. Tall layers can slide when too much soft buttercream is placed between them.
- Chill the crumb-coated cake for 20–30 minutes before the final frosting coat. This makes straight sides and square corners much easier.
- Always make one test ganache drip before decorating the entire cake.
- Add wafers shortly before serving because moisture gradually softens them.
- For clean slices, use a sharp knife and wipe it between cuts.
- Decoration quantities can be adjusted depending on the exact appearance desired.
- Prep Time: 1 hour 20 minutes
- Chilling/Cooling Time: 1 hour 30 minutes
- Cook Time: 30 minutes
- Category: Dessert
- Method: Baking
- Cuisine: American-inspired