Yule Log

Ingredients

• 6 large eggs
• 0.75 cups granulated sugar
• 1 tsp vanilla extract
• 0.5 cups all-purpose flour
• 0.25 cups unsweetened cocoa powder
• 0.25 tsp kosher salt
• 0.25 cups confectioners' sugar – for dusting towel
• 0.5 cups water
• 0.25 cups granulated sugar
• 3 tsp instant espresso powder
• 1 tbsp dark rum
• 4 large egg yolks
• 0.25 cups water
• 0.75 cups granulated sugar
• 1 cups unsalted butter – softened, cut into pieces
• 8 ounces bittersweet chocolate – finely chopped
• 1 cups heavy cream
• 1 tbsp unsalted butter
• confectioners' sugar – for serving

Instructions

1. Preheat the oven to 375°F (190°C). Line a 10×15-inch jelly-roll pan with parchment, allowing overhang on the long sides.
2. Make the sponge: In a stand mixer with the whisk (or using a hand mixer), beat the eggs and 0.75 cup granulated sugar on medium-high until very thick, pale, and tripled in volume, 5–7 minutes. Beat in the vanilla extract. Sift together the all-purpose flour, unsweetened cocoa powder, and kosher salt, then gently fold the dry ingredients into the egg mixture in 3 additions until no streaks remain. Spread evenly into the prepared pan.
3. Bake until the cake springs back lightly in the center and just pulls from the edges, 10–12 minutes. Meanwhile, dust a clean kitchen towel generously with confectioners' sugar.
4. Turn the hot cake out onto the sugared towel, peel off the parchment, and trim any crisp edges. Starting from a short side, roll the warm cake up with the towel into a snug spiral. Cool seam-side down until just barely warm, about 30 minutes.
5. Make the coffee syrup: In a small saucepan, combine the water (0.5 cup) and 0.25 cup granulated sugar. Bring to a simmer, stirring to dissolve, 1–2 minutes. Off heat, stir in the instant espresso powder (use 1 tsp for the syrup and reserve the remaining 2 tsp for the buttercream) and the dark rum. Cool to room temperature.
6. Make the coffee buttercream: In a stand mixer, beat the egg yolks on medium until thick and lightened, 2–3 minutes. In a small saucepan, bring the water (0.25 cup) and 0.75 cup granulated sugar to a rapid boil; cook until 240°F (115°C), 3–5 minutes. With the mixer running on medium, slowly stream the hot syrup down the side of the bowl into the yolks. Increase to medium-high and beat until the bowl feels cool, 5–7 minutes. With the mixer on medium, add the unsalted butter (1 cup) a piece at a time until smooth and satiny. Beat in the reserved espresso powder until evenly flavored.
7. Make the ganache: Place the bittersweet chocolate in a heatproof bowl. Heat the heavy cream just to a simmer; pour over the chocolate along with the unsalted butter (1 tbsp). Let stand 2 minutes, then stir gently until glossy and smooth. Cool, stirring occasionally, until thickened and spreadable, 20–30 minutes.
8. Assemble the log: Carefully unroll the cake. Brush the surface evenly with the coffee syrup. Spread the coffee buttercream over the cake in an even layer to within 0.5 inch of the edges. Re-roll the cake without the towel, seam-side down.
9. Create a branch and frost: Trim the ends. Cut a short 3-inch piece from one end at a 45° angle and attach it to the side of the log with a little buttercream to form a branch. Spread the ganache over the log and branch. Drag the tines of a fork through the ganache to create bark-like ridges. Chill until set, about 30 minutes.
10. Finish and serve: Dust the log lightly with confectioners' sugar and transfer to a platter. Slice with a sharp, warm knife and serve.