We had this as on eof our Christmas desserts this year, and it was AMAZING! It was the yummiest thing on the table, and looked really impressive too. From the Family Circle cookbook, "Tastes Of Christmas".
Brush a 30x35cm Swiss roll tin with oil or melted butter and line the base and sides with baking paper.
Preheat the oven to 180C,.
Sift the flour and cocoa powder together twice.
Using electric beaters, beat the eggs and sugar for 5 minutes, or until light and fluffy and increased in volume.
Sift the flour mixture over the eggs and pour the butter around the edge of the bowl. Using a large metal spoon, gently fold the mixture together to incorporate the flour and butter. Take care not to over mix and lose too much volume.
Spread the mixture into th eprepared tin and bake for about 12 minutes, or until the sponge springs back to the light touch.
Sprinkle the extra caster sugar over a clean tea towel.
Turn the sponge out onto the tea towel, close to one end, leaving th epaper on the cake. Roll up the sponge and tea towel together and leave to cool completely.
To make the filling, put the white chocolate in a small heatproof bowl. Bring a small pan of water to the boil, then remove from the heat. Add the cream to the chocolate and stand the bowl over the pan of water, making sure the the base of the bowl does not touch the water, until the chocolate is soft. Stir until smooth.
Repeat with the dark chocolate and the cream for the topping.
Leave the white chocolate mixture until it has cooled to room temperature and is the consistency of cream.
Leave the dark chocolate mixture until it cools to a spreadable consistency.
Using electric beaters, beat the white chocolate mixture until soft peaks form- do not overbeat.
unroll the sponge, remove the tea towel and paper and spread with the filling, finishing 2cm from the end. Sprinkle with the hazelnuts. Re-roll the sponge, and trim the ends. Cut one end off on the diagonal and place it alongside the log to create a branch.
Place the roll onyo a serving platter, and spread the dark chocolate topping all over it.
Run the tines of a fork along the length of the roll, to give a 'bark" effect.
Just before serving, dust generously with icing sugar. Decorate with fresh green leaves.