A classic rolled cocoa sponge filled with coffee Swiss meringue buttercream and finished with chocolate ganache bark.
Ingredients
Cocoa sponge
200 g whole eggs
120 g granulated sugar
60 g cake flour
25 g unsweetened cocoa powder
15 g cornstarch
2 g fine sea salt
20 g whole milk
25 g unsalted butter, melted
5 ml vanilla extract
Coffee syrup
80 ml water
60 g granulated sugar
4 g instant espresso powder
10 ml dark rum (optional)
Coffee Swiss meringue buttercream
100 g egg whites
160 g granulated sugar
1 g fine sea salt
225 g unsalted butter, softened
8 g instant espresso powder
15 ml hot water
5 ml vanilla extract
Chocolate ganache
200 g dark chocolate (55–60% cacao), finely chopped
200 g heavy cream (35% fat)
20 g unsalted butter
1 g fine sea salt (optional)
For pan and finish
5 g unsalted butter, for greasing
20 g icing sugar, divided
5 g unsweetened cocoa powder, for dusting
Steps
Preheat the oven to 190°C.
Line a 33 × 45 cm rimmed baking sheet with parchment.
Grease the parchment lightly with 5 g butter.
Sift the cake flour, cocoa powder, cornstarch, and salt into a bowl.
Set the dry mixture aside.
Combine the eggs, granulated sugar, and vanilla in a large heatproof bowl.
Set the bowl over a pot of simmering water.
Whisk the egg mixture until warm to 40–43°C.
Remove the bowl from the heat.
Whip the egg mixture with a mixer on high until thick and forms a ribbon, 4–6 minutes.
Melt the 25 g butter in a small pan.
Warm the milk in the same pan until steaming.
Sprinkle one-third of the dry mixture over the whipped eggs.
Fold gently with a spatula until just combined.
Sprinkle half of the remaining dry mixture over the batter.
Fold gently until just combined.
Sprinkle the remaining dry mixture over the batter.
Fold gently until just combined.
Mix the warm milk and melted butter in a small bowl.
Stir 60 g of batter into the milk-butter mixture.
Fold the milk-butter mixture back into the main batter.
Pour the batter into the prepared pan.
Spread the batter evenly to the corners with an offset spatula.
Tap the pan once on the counter.
Bake the sponge until springy and just set, 10–12 minutes.
Dust a clean tea towel evenly with 10 g icing sugar.
Remove the sponge from the oven.
Run a knife around the edges of the sponge.
Invert the sponge onto the sugared towel.
Peel off the parchment.
Roll the sponge up with the towel from the short side.
Cool the rolled sponge to room temperature, 45–60 minutes.
Combine the water and granulated sugar for the syrup in a small saucepan.
Bring the syrup to a simmer.
Remove the syrup from the heat.
Stir in the espresso powder and rum.
Cool the syrup to room temperature.
Combine the egg whites, granulated sugar, and salt for the buttercream in a heatproof bowl.
Set the bowl over a pot of simmering water.
Whisk the mixture until it reaches 71°C and the sugar dissolves.
Transfer the bowl to a stand mixer fitted with the whisk.
Whip on medium-high until glossy and room temperature, 8–10 minutes.
Add the softened butter a few pieces at a time with the mixer running.
Beat the buttercream until smooth and fluffy.
Dissolve the espresso powder in 15 ml hot water.
Cool the coffee concentrate to room temperature.
Beat the coffee concentrate and vanilla into the buttercream.
Chop the chocolate finely for the ganache.
Heat the cream in a saucepan until it just simmers.
Pour the hot cream over the chopped chocolate in a bowl.
Let the mixture stand for 2 minutes.
Add the butter and salt to the bowl.
Stir the ganache gently until smooth and glossy.
Cool the ganache until spreadable, 20–30 minutes.
Unroll the cooled sponge carefully.
Brush the cake surface evenly with coffee syrup.
Spread two-thirds of the buttercream over the cake, leaving a 15 mm border.
Roll the cake up tightly from the same short side.
Wrap the log in parchment.
Chill the log for 20 minutes.
Unwrap the log.
Trim 1–2 cm from both ends for clean edges.
Cut a short diagonal slice from one end to make a branch.
Attach the branch to the side of the log with a dab of buttercream.
Place the log on a serving board.
Spread the ganache over the log and branch.
Create bark texture by dragging a fork or spatula along the ganache.
Dust the log lightly with cocoa powder.
Sift the remaining 10 g icing sugar over the log for a snowy effect.
Chill the cake for 20 minutes to set the ganache.
Bring the cake to room temperature before serving.
Notes
Technique keys: Whip the egg foam to full ribbon for structure, then fold minimally to preserve air; roll the sponge while warm to set the curl; moisten the sponge with syrup to prevent cracking and dryness; cool the ganache to a spreadable state for clean bark texture.
Make-ahead: Bake and roll the sponge up to 1 day ahead wrapped airtight. Prepare buttercream and ganache up to 2 days ahead and bring to spreading consistency before assembly. The finished bûche keeps 2 days refrigerated; serve at cool room temperature.
Variations: Fill with chestnut cream (crème de marrons + whipped cream), hazelnut praline buttercream, or chocolate whipped ganache. Flavor the syrup with orange liqueur, brandy, or vanilla.
Decorations: Add meringue mushrooms, sugared cranberries, or rosemary sprigs for a woodland finish. For mushrooms, pipe stiff French meringue into caps and stems, bake low and slow, then glue with melted chocolate.
Cooksmith