Buche De Noel

Ingredients

• 5 large eggs – at room temperature
• 0.75 cup granulated sugar
• 1 tsp vanilla extract
• 0.75 cup cake flour – sifted
• 0.25 cup unsweetened cocoa powder – sifted
• 0.25 tsp fine sea salt
• 2 tbsp unsalted butter – melted and cooled
• 0.25 cup powdered sugar – for dusting towel
• 0.5 cup water
• 0.25 cup granulated sugar – for soaking syrup
• 1 tbsp dark rum
• 0.5 tsp vanilla extract – for soaking syrup
• 4 ounces bittersweet chocolate – finely chopped
• 4 large egg whites
• 1 cup granulated sugar – for buttercream
• 1 cup unsalted butter – cut into pieces, at cool room temperature
• 1 tsp vanilla extract – for buttercream
• 0.25 tsp fine sea salt – for buttercream
• powdered sugar – for serving
• meringue mushrooms – for serving

Instructions

1. Preheat the oven to 400°F. Line a 10×15-inch jelly roll pan with parchment paper, letting it overhang on the long sides for easy lifting.
2. Sift the cake flour, cocoa powder, and 0.25 tsp fine sea salt together and set aside.
3. In a large bowl or stand mixer, whip the 5 eggs, 0.75 cup granulated sugar, and 1 tsp vanilla on high speed until tripled in volume and thick ribbons fall from the whisk, 8–10 minutes.
4. Sprinkle the dry mixture over the egg foam in three additions, gently folding with a spatula just until no flour streaks remain. Fold in the 2 tbsp melted butter until just incorporated.
5. Spread the batter evenly into the prepared pan and smooth the top. Bake until the cake springs back lightly in the center and the edges just pull away, 10–12 minutes.
6. While the cake bakes, lay a clean kitchen towel on the counter and dust it evenly with the 0.25 cup powdered sugar.
7. Immediately invert the hot cake onto the sugared towel and peel off the parchment. Starting from a short side, roll the cake and towel up together into a snug log. Set seam-side down to cool until barely warm, 30–45 minutes.
8. Make the soaking syrup: In a small saucepan, bring 0.5 cup water and 0.25 cup granulated sugar to a simmer, stirring to dissolve, 2–3 minutes. Remove from heat, cool to lukewarm, then stir in 1 tbsp dark rum and 0.5 tsp vanilla.
9. Make the buttercream: Melt the 4 oz chopped bittersweet chocolate gently (double boiler or microwave at 50% power), then cool to just lukewarm. In a heatproof bowl, whisk 4 egg whites with 1 cup granulated sugar over a simmering water bath until the sugar dissolves completely and the mixture reaches 160°F, 3–5 minutes. Transfer to a mixer and whip on high until glossy, stiff peaks form and the bowl is cool to the touch, 7–10 minutes.
10. With the mixer on medium, add 1 cup unsalted butter, a few pieces at a time, beating until smooth and satiny. Beat in 1 tsp vanilla and 0.25 tsp fine sea salt, then pour in the cooled melted chocolate and mix until fully combined and silky.
11. Assemble: Carefully unroll the cooled cake. Brush the surface lightly and evenly with the rum syrup (you may not need all of it). Spread an even layer of buttercream over the cake, leaving a 0.5-inch border on the long far edge.
12. Roll the cake back up without the towel, ending with the seam down. Trim a thin slice from both ends to tidy. Cut a short diagonal slice from one end and attach it to the side of the log with a dab of buttercream to form a stump.
13. Coat the outside of the log and stump with the remaining buttercream. Drag the tines of a fork along the buttercream to create bark-like ridges. Chill until firm, about 30 minutes.
14. Just before serving, lightly dust the log with powdered sugar (for serving) and decorate with meringue mushrooms (for serving) if desired. Slice with a warm, clean knife.