Ingredients

• 4 free-range eggs
• separated
• 60g/2¼oz caster sugar
• 60g/2¼oz plain flour
• 15g/½oz unsalted butter
• melted
• 70g/2¾oz caster sugar
• 3 free-range egg yolks
• 30ml/1¼fl oz dark rum
• 240g/8¾oz unsalted butter
• softened to room temperature
• 200g/7oz candied chestnuts
• half reserved whole
• the remainder roughly chopped
• 40g/1¼oz caster sugar
• 25ml/1fl oz dark rum
• 2 tbsp milk
• 90ml/3fl oz whipping cream
• 80g/2¾oz plain chocolate
• minimum 70 per cent cocoa solids
• chopped
• plus extra grated chocolate
• to decorate
• cocoa powder
• to decorate

Directions

• For the genoise
• preheat the oven to 180C/160C Fan/Gas 4.
• Whisk the egg whites in a bowl (or free-standing mixer) until soft peaks form when the whisk is removed. Gradually add the sugar as you whisk the egg whites
• until stiff peaks form when the whisk is removed.
• Reduce the speed of the electric whisk to medium
• then whisk the egg yolks into the mixture
• one by one.
• Sift half of the flour into the bowl
• then gently fold it into the egg mixture using a spatula. Add the remaining flour and carefully fold it into the egg whites too.
• Pour over the melted butter and gently fold it into the egg white mixture.
• Line a 30cm/12in Swiss roll tin with silicone paper
• sticking each corner to the tin with a dab of the genoise mixture.
• Pour the genoise into the prepared tin
• pushing it into the corners and levelling the surface using a palette knife.
• Bake the genoise in the oven for 10 minutes
• or until it is pale golden-brown in colour and springy to the touch. Remove from the oven and set aside to cool in the tin.
• Meanwhile
• for the buttercream
• heat the sugar and 50ml/2fl oz water in a small saucepan until the temperature of this sugar syrup reaches 121C (use a sugar thermometer for this).
• Using an electric whisk or free-standing mixer
• whisk the egg yolks with 30ml/1fl oz water for 5 minutes on full speed until pale and fluffy.
• Reduce the speed of the electric beaters
• then drizzle the sugar syrup in a thin stream down the side of the bowl. (Caution: do not pour the hot syrup directly onto the beaters). Whisk until the mixture thickens and looks silky
• then continue to whisk until the mixture cools completely.
• Reduce the speed of the beaters to a slow speed
• then whisk in the rum. Add the softened butter a little at a time
• whisking until each addition has become fully incorporated into the sabayon
• then continue to whisk for a further 3 minutes.
• Fold in the chopped chestnuts and set aside until needed (chill in the fridge if making in advance).
• For the soaking liquid
• bring the sugar and 40ml/1¼fl oz water to the boil in a small saucepan
• then remove the pan from the heat and stir in the rum.
• Using a pastry brush
• brush the soaking liquid evenly over the cooled sponge.
• Turn the soaked sponge upside down onto a clean tea towel
• then carefully peel away the silicone paper.
• Spread one-third of the buttercream in an even layer all over the soaked sponge. Place the candied chestnuts in a line where the inside of the roll will be. Then roll the sponge as tightly as possible using the tea towel to lift the sponge.
• Wrap the sponge roll tightly in cling film
• then chill in the fridge for 15 minutes.
• Unwrap the sponge roll and transfer it to a cake board with the seam on its underside. Carefully trim each end using a sharp knife.
• Spread the remaining buttercream all over the sponge roll in an even layer using a palette knife (or piping bag
• if desired). Drag a fork lightly and unevenly through the buttercream to make it look like tree bark. Refrigerate for a further 30 minutes.
• Meanwhile
• for the chocolate sauce
• bring the milk and cream just to the boil in a saucepan. Remove the pan from the heat and stir in the chocolate until smooth and melted.
• Just before serving
• dust the bûche de Noël with a little cocoa powder and garnish with grated chocolate or chocolate curls. If desired
• slice the end off the log and place it on top.
• To serve
• slice the bûche de Noël and drizzle with a little of the chocolate sauce.