Belgian Chocolate Birthday Cake

Preparation

1. Step 1

   Preheat the oven to 350°F. Spread the nuts on a baking sheet. Bake until fragrant and toasted, about 12 minutes. Transfer to a clean kitchen towel; rub to loosen the skins. Butter a 9 × 3-inch springform pan well; coat with cocoa, tapping out any excess.

   Step 2

   In a food processor, grind the nuts with the granulated sugar until fine but not pasty; transfer to a large bowl; stir in the flour, baking soda, and salt.

   Step 3

   In a heatproof bowl, whisk together the cocoa and boiling water until smooth. (The mixture will thicken as it cools.)

   Step 4

   In the bowl of an electric mixer, cream the butter and brown sugar on high until lightened and fluffy, 3 to 4 minutes. Beat in the eggs 1 at a time until well blended.

   Step 5

   Stir the buttermilk and vanilla into the cocoa mixture. Mixing on low, add half the dry ingredients to the creamed mixture; when blended, pour in the cocoa mixture, and add the remaining dry mixture, mixing just until incorporated. Scrape the batter into the prepared pan; smooth the top. Bake 1 hour to 1 hour and 10 minutes, until a tester inserted in the center comes out clean. Let cool in the pan for 10 minutes; remove from the pan and cool completely. Place the cooled cake on a 9-inch cardboard round.

   Step 6

   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.

   Step 7

   Spread the whipped ganache smoothly on the top and sides of the cooled cake, and chill the cake. Gently stir the remaining ganache every 5 minutes until thickened and cool.

   Step 8

   Place the cake (still on the cardboard round) on a wire rack over a sheet of waxed or parchment paper. Working with a small ladle, pour the ganache over the top of the cake, moving the ladle in a circular fashion while in contact with the cake, letting the ganache run down the sides. Scrape up the excess and reserve for another use. Let the cake stand at room temperature until set. Garnish with nuts and chocolate curls.

2. Candied Hazelnuts and Chocolate Curls

   Step 9

   Preheat the oven to 350°F. Spread the nuts on a baking sheet. Bake until fragrant and toasted, about 12 minutes. Transfer to a clean kitchen towel; rub to loosen the skins.

   Step 10

   Place the 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 the nuts to the pan; stir with a wooden spoon until the caramel seizes around the nuts. Transfer to a parchment-lined baking sheet; let cool completely.

   Step 11

   Once the nuts are cool, place half the chopped chocolate in a deep, medium-size stainless-steel bowl. Place the bowl over a saucepan with 1 inch of simmering water; stir until the chocolate is melted and hot. Add the remaining chocolate to the bowl; remove the bowl from the pan of water; let stand about 5 minutes, and then stir until smooth.

   Step 12

   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 the surface). Let stand until just tacky. Hold the scraper at a 45-degree angle; scrape the chocolate off the surface. The curls can be stored in an airtight container layered with parchment at room temperature.

   Step 13

   While the chocolate sets, add the candied nuts to the remaining chocolate in the bowl, and stir until coated. Spread the nuts on a parchment-lined baking sheet, and let stand until set.

   Step 14

   Sift the cocoa powder on top of the dried nuts and toss to coat. Store in a resealable plastic bag for up to 1 week, until ready to use.