
A show-stopping Christmas centerpiece featuring a light chocolate sponge filled with rich hazelnut buttercream. Decorated with whimsical meringue mushrooms and a rustic bark texture, this festive log is as delicious as it is beautiful.
Start by making the meringue mushrooms (these can be prepared up to a week in advance). Preheat your oven to 120°C (100°C fan/gas ½) and line a baking tray with parchment paper. In a clean glass bowl, whisk the 2 egg whites using an electric mixer until they form stiff peaks. Gradually add the sugar, one tablespoon at a time, whisking constantly until the mixture is thick, glossy, and holds its shape.
Transfer the meringue to a piping bag with a large round nozzle. Pipe 12–15 mushroom caps by squeezing out small, squat circles onto the tray. Pipe an equal number of short vertical lines for the stems. Use a wet finger to gently dab down any sharp peaks. Lightly dust the caps with cocoa powder and bake for 1 hour. Turn off the oven and let them cool completely inside with the door closed.
For the sponge, increase the oven temperature to 180°C (160°C fan/gas 4). Line a 32 x 22cm Swiss roll tin with parchment paper. Whisk the 5 egg whites to stiff peaks, then gradually beat in half of the caster sugar until glossy. In a separate bowl, whisk the 5 egg yolks with the remaining caster sugar and vanilla until pale and fluffy. Stir in the chocolate hazelnut spread, then gently fold in the egg whites in three batches.
Sift the flour, 2 tbsp cocoa powder, and a pinch of salt over the egg mixture. Fold very gently until just combined, being careful not to deflate the air. Pour the batter into the prepared tin, spreading it to the corners. Bake for 12–15 minutes until the sponge is springy to the touch. Immediately cover the hot sponge with a fresh sheet of parchment and a clean, damp tea towel; let it cool completely in the tin.
Prepare the buttercream by beating the softened butter until smooth. Gradually add the icing sugar, 1 tbsp of milk, and a drop of vanilla, whisking for 1 minute until creamy. Invert the cooled sponge onto the towel and remove the tin. Score a light line 1cm from one long edge (do not cut through). Spread about one-third of the buttercream over the sponge, leaving a small border, then roll it up tightly starting from the scored edge.
Trim an 8cm slice from the roll at a slight angle and attach it to the side of the main log to create a 'branch' effect. Mix the remaining cocoa powder and the last tablespoon of milk into the leftover buttercream. Spread this chocolate frosting over the entire log. Use a fork to drag long lines through the frosting to create a realistic bark texture.
Assemble the mushrooms by using a little melted dark chocolate to stick the stems to the caps. Arrange the mushrooms on and around the log. Finish by scattering chopped hazelnuts and pumpkin seeds over the log to resemble forest debris. Store in an airtight container for up to 4 days.
To prevent the sponge from cracking, ensure you roll it while it is still slightly flexible or use the damp towel method as described. If the buttercream is too stiff, add an extra teaspoon of milk. The meringue mushrooms are moisture-sensitive, so add them just before serving if the environment is humid.