Bûche de Noël

Chocolate Truffle Bûche de Noël

Makes a 13" log, about 8 to 10 servings

Cake
•Yolks from 6 large eggs
•¾ cup sugar, divided
•Whites from 5 large eggs
•½ cup cocoa powder

Rum Syrup
•¼ cup water
•1⁄3 cup sugar
•1⁄8 tsp. vanilla extract
•1 T dark rum

Chocolate Ganache
•Yolks from 5 large eggs
•½ cup plus 1 T sugar
•½ cup milk
•½ cup plus 2 T heavy cream
•9 oz. dark bittersweet chocolate, chopped
•2½ T cocoa powder
•½ cup hot water

Special equipment: 13" x 18" rimmed baking pan, instant-read thermometer

Directions

For the Cake:
Preheat oven to 375°F. Spray a 13" x 18" rimmed baking pan with nonstick spray and line with parchment paper. Using the whisk attachment, beat the egg yolks with 6 T of the sugar at high speed until the mixture is pale and fluffy, about 3 minutes; transfer to a large bowl. In a separate bowl, beat egg whites at high speed until soft peaks form. Gradually add the remaining 6 T of sugar and continue beating until the whites are stiff and glossy. Using a rubber spatula, stir one fourth of the beaten whites into the yolk mixture, then fold in the remaining whites until no streaks remain. Sift the cocoa over the batter and fold gently until fully incorporated. Spread the batter evenly on the prepared baking sheet. Bake for 10 to 15 minutes, rotating the pan halfway through, until the cake feels springy and dry. Transfer cake and parchment paper to a rack and let cool.

For the Rum Syrup:
In a small saucepan, combine the water, sugar, and vanilla, and simmer until sugar is dissolved. Remove from the heat and stir in the rum. Let cool.

For the Chocolate Ganache:
In a heatproof bowl, whisk egg yolks with sugar until smooth. In a medium saucepan over medium-low heat, combine the milk and cream and bring to a simmer. While whisking the eggs constantly, pour in the hot-milk mixture in a slow stream. Transfer back to the saucepan and place over low heat. Cook, whisking constantly, until the mixture thickens enough to coat the back of a spoon, but does not simmer (185°F on the thermometer). Pour the cream mixture over the chocolate in a separate heatproof bowl and stir until chocolate is melted, making a ganache. In a small bowl, stir the cocoa powder into the hot water until dissolved and then stir into the ganache. Transfer ganache to the refrigerator to set, about 2 hours.

To Assemble:
Transfer the cake (with parchment paper) to a flat surface and brush rum syrup evenly over top, allowing it to absorb. Spread half of the ganache evenly on the cake. Begin rolling cake to form a 13"-long log, pulling away the parchment paper as you roll. When cake is rolled up, place it on top of the paper, seam-side down. Fold the paper over the log with the ends facing you. Place a ruler or rimless baking sheet flush against the parchment and gently push forward against the cake to tighten the roll. Remove parchment and frost cake with the remaining ganache. Refrigerate. If desired, garnish the cake with cocoa powder, chocolate shavings, and meringue kisses.