Ingredients:
Cake:
- 4 ounces hazelnuts
- 13 1/3 tablespoons unsalted butter (1 2/3 sticks), softened
- 2/3 cup Dutch-process cocoa powder
- 6 tablespoons granulated sugar
- 1 2/3 cup all-purpose flour
- 1 1/2 teaspoons baking soda
- 1/4 teaspoon table salt
- 2/3 cup boiling water
- 1 3/4 cups packed dark-brown sugar
- 4 large eggs, at room temperature
- 1 1/3 cups buttermilk, at room temperature
- 2 1/2 teaspoons pure vanilla extract
Ganache:
16 oz. bittersweet or semisweet chocolate, very finely chopped.
2 1/2 cups heavy cream
Candied Hazelnuts and Chocolate Curls:
2 cups hazelnuts
1 cup granulated sugar
2 Tbsp water
16 oz. bittersweet chocolate, very finely chopped
1/4 cup unsweetened chocolate
Directions:
Cake*:
- Preheat oven to 350 degrees. Place nuts on a baking sheet. Bake until fragrant and toasted, about 12 minutes. Transfer to a clean kitchen towel; rub to loosen skins. Butter a 9-by-3-inch springform pan well; coat with cocoa, tapping out any excess. Step 1
- In a food processor, grind nuts with granulated sugar until fine but not pasty; transfer to a large bowl; stir in the flour, baking soda, and salt. Step 2
- In a heat-proof bowl, whisk together cocoa and boiling water until smooth. (Mixture will thicken as it cools.) Step 3
- In the bowl of an electric mixer, cream butter and brown sugar on high until lightened and fluffy, 3 to 4 minutes. Beat in eggs one at a time until well blended. Step 4
- Stir buttermilk and vanilla into cocoa mixture. Mixing on low, add half of dry ingredients to creamed mixture; when blended, pour in the cocoa mixture, and add remaining dry mixture, mixing just until incorporated. Scrape batter into prepared pan, smooth top. Bake 1 hour to 1 hour and 10 minutes, until a tester inserted in the center comes out clean. Let cool in pan for 10 minutes; remove from pan and cool completely. Place cooled cake on a 9-inch cardboard round. Step 5
- Place half the ganache in a bowl; place in a larger bowl of ice water; whip with a balloon whisk until lighter in color and spreadable, removing bowl from ice bath and returning it as necessary. Step 6
- Spread the whipped ganache smoothly on top and sides of cooled cake, and chill the cake. Gently stir remaining ganache every 5 minutes until thickened and cool. Step 7
- Place cake (still on cardboard round) on a wire rack over a sheet of waxed or parchment paper. Working with a small ladle, pour ganache over top of cake, moving the ladle in a circular fashion while in contact with the cake, letting the ganache run down sides. Scrape up excess and reserve for another use. Let cake stand at room temperature until set. Garnish with nuts and chocolate curls. Step 8
Ganache:
- Chop chocolate finely using a serrated knife; place in a large heat-proof bowl. Step 1
- Bring cream to a boil over medium-high heat; pour directly over chopped chocolate. Allow to sit 10 minutes. Use a rubber spatula to gently stir chocolate and cream until well combined and smooth. Let sit at room temperature until cooled and just thickened, stirring occasionally, about 30 minutes, but up to an hour depending on the temperature of the room. Step 2
Candied Nuts and Curls:
- Step 1
Preheat oven to 350 degrees. Place nuts on a baking sheet. Bake until fragrant and toasted, about 12 minutes. Transfer to a clean kitchen towel; rub to loosen skins. Place sugar and water in a medium heavy skillet. Stir with a fork over medium-high heat until dissolved; let boil undisturbed for 3 minutes. Add nuts to pan; stir with wooden spoon until caramel seizes around nuts. Transfer to parchment-lined shallow baking sheet; let cool.
- Once nuts are cool, place half of chopped chocolate in a deep medium-size stainless-steel bowl. Place bowl over a saucepan with 1 inch of simmering water; stir until chocolate is melted and hot. Add remaining chocolate to bowl, remove bowl from pan of water, let stand about 5 minutes, then stir until smooth. Step 2
- Pour half the chocolate onto an inverted baking sheet; spread with a bench scraper until 1/8 inch thick or slightly thinner (chocolate should be opaque on surface). Let stand until just tacky. Hold scraper at a 45º angle; scrape chocolate off surface. Store curls at room temperature in an airtight container layered with parchment. Step 3
- While chocolate sets, add candied nuts to remaining chocolate in bowl, and stir until coated. Spread nuts on a parchment lined baking sheet, and let stand until set. Step 4
- Sift cocoa powder on top of dried nuts and toss to coat. Store in a resealable plastic bag for up to 1 week, until ready to use. Step 5
*Cook's Notes:
Toast and peel the nuts for the cake and garnish at the same time. Bake the cake up to three days ahead; wrap well and keep at room temperature. The candied hazelnuts and chocolate curls can also be made three days ahead; store in airtight containers.