Preheat the oven to 200 degrees Celsius, fan oven setting. Grease and line the base and sides of two 25 x 30cm Swiss roll baking trays with parchment paper.
Sift together the flour and cocoa powder.
Use an electric beater to whisk the eggs and sugar together until pale and fluffy and doubled in volume.
Drizzle the hot water down the side of the mixing bowl.
Turn off the mixer and gently fold in the flour with a spatula or metal spoon. Pour the mixture into the baking trays, dividing it as evenly as you can. Gently smooth the
surface with a spatula.
Bake for 10-12 minutes until the surface of the sponge feels dry when patted.
Tear off two large sheets of parchment paper and sprinkle with caster sugar.
As soon as the sponges come out of the oven, turn them out onto the paper. Using the paper as a guide, roll each sponge from a short side into a log. Cover with tea towels and allow to cool completely.
To make the hazelnut cream, beat together the fresh cream, icing sugar and hazelnut liqueur until just stiff but still spreadable.
To make the chocolate coating, simply place the chocolate in a glass bowl over a bowl of simmering water until completely smooth and melted. Stir with a spatula.
Unroll the sponge on a clean work surface. Sprinkle over half the crushed hazelnuts. Using a spatula, spread half the cream over the sponge, leaving a 2cm boarder at the end. Roll the sponge tightly into a log. Repeat with the second sponge.
To assemble the chocolate log, place one sponge on a baking tray lined with a silicone baking sheet. Cut the second sponge in half on the diagonal. Place this on top on the first log to form a protruding ‘branch’. This should sit quite securely, but if you are nervous, you can insert a long bamboo skewer to keep in in place. Serve the second half of the unused sponge log in slices with fresh raspberries.
To create the chocolate bark, spoon the melted chocolate all over the log, smoothing it gently with the back of the spoon. The chocolate will pool underneath, but don’t worry. Place in a cool place, but not the fridge, and leave it until the chocolate sets completely. Once the chocolate is hard, use a toothpick or a fork to draw lines in the chocolate. Leave any chocolate curls as it will look more like rough bark.
To plate up, use a knife and trim the chocolate that has set and pooled under the Yule log. Place the Yule log on a serving platter and decorate with extra chopped nuts and fondant mushrooms to resemble the forest floor.