STEP 1: PREPARE THE CHOCOLATE SPONGE CAKE

Start by preheating your oven to 350°F (175°C) and line a 10×15-inch jelly roll pan with parchment paper. This is essential for ensuring the cake doesn’t stick and comes out easily after baking.

In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt. Set aside.

In a separate large mixing bowl, beat the eggs and sugar with an electric mixer on high speed until the mixture is pale, fluffy, and doubled in size—about 5-7 minutes. This will help create the light, airy texture of the cake. Add the vegetable oil and vanilla extract, then mix gently to combine.

Gradually sift in the dry ingredients, folding them in with a spatula until just combined. Finally, add the hot water to the batter, mixing gently to keep the batter airy.

Pour the batter into the prepared pan, smoothing it out evenly. Bake in the preheated oven for about 10-12 minutes, or until a toothpick inserted into the center of the cake comes out clean. The cake should spring back when gently pressed.

STEP 2: COOL THE CAKE

Once baked, remove the cake from the oven and immediately invert it onto a clean kitchen towel dusted with powdered sugar. Peel off the parchment paper carefully. While the cake is still warm, gently roll it up with the towel, starting from the short end. This step helps the cake retain its shape and prevents cracking when you unroll it later.

Let the cake cool completely, still rolled in the towel, for about 30 minutes. This allows the cake to set and makes it easier to work with when assembling.

STEP 3: MAKE THE CHOCOLATE BUTTERCREAM FILLING

While the cake is cooling, prepare the chocolate buttercream. In a large bowl, beat the softened butter on medium speed for about 3 minutes until it’s light and fluffy. Gradually add the powdered sugar, one cup at a time, mixing well after each addition.

Sift the cocoa powder into the mixture and add the vanilla extract. Continue mixing until fully incorporated. Finally, add the heavy cream and beat the buttercream until smooth and spreadable, about 2-3 minutes.

STEP 4: MAKE THE CHOCOLATE GANACHE

To make the ganache, heat the heavy cream in a small saucepan over medium heat until it begins to simmer. Once the cream is hot, pour it over the chopped chocolate in a heatproof bowl. Let it sit for 1-2 minutes, then whisk until the chocolate is fully melted and the ganache is smooth.

Allow the ganache to cool for about 10 minutes before using it to glaze the cake. It should have a pourable consistency but not be too runny.

STEP 5: ASSEMBLE THE BÛCHE DE NOËL

Once the cake has cooled completely, carefully unroll it from the towel. Spread an even layer of the chocolate buttercream filling over the surface, leaving about 1 inch of space at the edges. Roll the cake up again, this time without the towel, to form a log. Place the log seam-side down on a serving platter.

Use the remaining buttercream to cover the top and sides of the cake. Be sure to create a smooth finish, but don’t worry if the surface looks a little rustic. You can use a fork to create texture on the frosting to resemble bark.

STEP 6: DECORATE THE BÛCHE DE NOËL

To decorate your Bûche de Noël, pour the cooled ganache over the top of the cake, allowing it to drip down the sides. You want a shiny, smooth finish, so be sure to spread it evenly with a spatula.

Now comes the fun part—decorating! Dust the cake with powdered sugar to create a snowy effect. If you’re using marzipan mushrooms, place them on top for a whimsical touch. You can also add fresh holly leaves, edible flowers, or chocolate shavings for a festive finishing touch.

STEP 7: CHILL AND SERVE

Let the assembled Bûche de Noël chill in the fridge for at least 1 hour to set the ganache and allow the flavors to meld. Slice the cake into generous pieces, and enjoy!