This is adapted from “My Kind of Chocolate Birthday Cake,” Bon Appetit, June 2005. Tess Murdoch made it for Barry’s birthday this year, garnished with homemade candied orange peel and chocolate curls. It was as delicious as it was beautiful.
Cake
4 oz bittersweet chocolate, chopped
1/3 C dark brown sugar, packed
2 T unsalted butter
1/2 t grated orange peel
1/2 t coarse salt
2 eggs
2 T sugar
1 T flour
1/2 C hazelnuts, toasted, husked, and chopped
Filling
5 oz bittersweet chocolate, chopped
3 oz milk chocolate, chopped
1-1/2 C chilled heavy whipping cream (divided)
5 T unsalted butter, at room temperature
Glaze
1/2 C heavy whipping cream
1 T light corn syrup
4 oz bittersweet chocolate, chopped
1 T unsalted butter, room temperature
Garnish
Chocolate curls
Chopped toasted hazelnuts
Candied orange peel
For cake:
Preheat oven to 325 F. Line a 13x9x1 inch baking sheet with parchment paper, butter the parchment paper. Combine first 4 ingredients in medium metal bowl. Set it over a pan of barely simmering water, stirring until the chocolate and butter melt. Remove from water and stir in salt.
Beat eggs and 2 T sugar in another bowl until pale (about 6 min). Fold into chocolate mixture. Fold in flour, then hazelnuts. Spread the batter evenly on the baking sheet. Bake for 13 minutes, or until toothpick inserted into center comes out with a few moist crumbs attached. Set the pan on a rack to cool. The cake will be large and low.
For filling:
Combine the chocolates in a medium metal bowl. Bring 1 C cream to a simmer in a small saucepan; pour it over the chocolates and let stand for a minute. Stir until melted and smooth. Chill for about 2 hours, until firm.
Place the bowl with the chilled chocolate mixture over a saucepan of barely simmering water until it’s partly melted — but don’t stir it. This will take about 5 minutes. Remove from the water, add the butter. Using an electric mixer, beat until filling is thick and glossy, about 3 minutes. Clean and dry the beaters, and beat 1/2 C chilled whipping cream in another bowl until peaks form. Fold the whipping cream into the filling.
Cover a 14×5-inch piece of cardboard with foil. Invert the cake onto a work surface and remove parchment. Cut it lengthwise in half. Place one half on the cardboard and spread with 1/2 C of the chocolate filling. Top with the second cake half. Spoon the remaining filling into a pastry bag fitted with large plain round tip. Pipe filling atop cake in side-by-side lengthwise rows, then smooth the top. Chill until filling is firm, about an hour.
For glaze:
Bring cream and corn syrup to simmer in a small saucepan. Remove from heat. Add the chocolate, let stand 5 minutes. Stir until smooth. Add the butter, stir until melted. Let this stand until barely lukewarm but still pourable, about 20 minutes.
Place the cardboard with the cake on it on a rack that is set over a rimmed baking sheet. Spoon the glaze over the cake, allowing it to run down the sides. Smooth it over the sides with a spatula. Garnish with chocolate curls, nuts, and candied orange peel.
Refrigerate until the glaze is set, at least 2 hours.