Start this recipe by whisking the egg with the sugar till thick, pale and light for 5-7 minutes. Fold in the melted chocolate followed by the ground hazelnuts and 2 tbsp four. Pour the mixture into a lined swiss roll tin ( 34cm x 23cm approx) and bake in the oven at 180` for 15 minutes or until cooked through. Allow to cool down. Meanwhile, make the filling by whipping the cream to soft peaks. Add in the cooled melted chocolate and continue to whisk till incorporated. Use this mixture to fill the sponge, cover with 2/3 of the fresh blackberries and roll up. Place in the fridge to set for at least an hour. When ready to assemble, trim the ends off the roulade diagonally and place onto your serving board. Drizzle over the extra melted chocolate and drip down the sides. Quickly cover the top the chocolate shavings and place on the remaining blackberries and berries to decorate. Dust the top with icing sugar and serve.