Method 
1. Preheat oven 180°C. Grease a 30cm by 35cm Swiss roll tin and line with baking paper.
2. For Yule log, beat eggs and sugar in an electric mixer for 5 minutes or until light and fluffy.
3. Sift flour and cocoa together and then sift over the eggs. Pour butter around the edge of the bowl and using a large metal spoon gently fold mixture together. Pour mixture into prepared tin, spread out gently using a palette knife and bake for 12-15 mins or until sponge springs back. Cover with a clean tea towel.
4 .For filling, place cream and white chocolate in a heat proof bowl over simmering water. Stir until chocolate has melted and become smooth. Refrigerate until the consistency of thick cream.
5. For topping, place cream and dark chocolate in a heat proof bowl over simmering water. Stir until chocolate has melted and become smooth. Refrigerate until the consistency of thick cream.
6. Beat white chocolate ganache in an electric mixer, until soft peaks form. Spread filling to the end of roll, leaving a 3cm gap at the end. Sprinkle hazelnuts over filling. Roll and trim sponge. Cut off one end piece about 10cm long on the diagonal and place it alongside the log to create a branch.
7. Place yule log on a serving platter and spread the dark chocolate topping all over it and score with a fork. Dust with icing sugar and decorate with a sprig of redcurrants and some holly leaves.
