Ingredients:
For the Cake:
- 6 large eggs, separated
- 150g caster sugar
- 45g cocoa powder
- 1 1/2 tsp vanilla extract

For the icing:
- 180g dark chocolate, melted
- 250g icing sugar
- 245g softened butter
- 1 tbsp vanilla extract
FOR THE CAKE: Preheat the oven to 180C/320F/gas mark 4.
In a bowl, whisk the egg whites until stiff. Add in one third (50g) of the sugar and whisk until the mix holds stiff peaks. In a separate bowl, whisk the yolks with the rest of the sugar until pale and thick. Add the vanilla extract and sieve the cocoa powder and mix until well blended. Fold the egg whites into the chocolate mixture, and mix until smooth.
Line a swiss roll tin with baking paper, and pour in the mixture. Bake it for 20 minutes, until the cake is ready.

FOR THE ICING: Melt the dark chocolate. In a separate bowl, cream together the icing sugar and butter until smooth. Add the melted chocolate, and vanilla, mix until well blended.
When the cake is out and cooled, add a thin layer of the icing onto the cake and carefully roll it into a log shape. Coat it in the rest of the icing, and use a fork to make bark patterns, and dust it in icing sugar.

ENJOY!
