• Preheat oven to 180°C.
• Line a 22cm x 33cm rectangular baking tray with baking paper with a 3cm overhang.

For the Cake

• Place the dark chocolate and 30g milk in glass bowl. Microwave in short 20 second bursts until the chocolate softens. Stir until well combined. Set aside to cool.
• Place egg yolks, oil, 40g milk, vanilla and half the sugar in a bowl. Whisk until combined. Set aside. Sift in the flour.
• In the bowl of a stand mixer, fitted with a whisk attachment, whisk the egg whites until soft peaks form. While still mixing, squeeze in the lemon juice and slowly drizzle the remaining sugar. Whisk until stiff peaks form.
• Fold a third of the egg whites into the egg yolk mixture, followed by the remaining whites – taking care not to beat the air out.
• Remove a third of the mixture into a separate bowl and fold in the cooled chocolate as lightly as possible.
• Spread the vanilla cake mixture evenly onto the lined baking tray. Smooth the surface with a pallet knife. Dollop the chocolate mixture over the top and spread it out lightly. Using the back of a spoon, marble the cake batter.
• Bake in the oven for 20-25 minutes or until the cake is just cooked through. Remove from the tin onto a wire rack.
• Place baking paper or a clean, slightly damp clean tea towel over the cake followed by a tray. Quickly and carefully flip the cake over over, placing the shorter end facing you.
• While the cake is still warm, remove the bottom baking paper and carefully roll the cake up from the end facing you to the top. Wrap the roll in baking paper and chill in the fridge.

For the Cream Filling

• In the bowl of a stand mixer fitted with a whisk attachment, whisk the cream, sugar, vanilla and sherry until just past soft peaks.
• Fold in the chocolate. Set aside in the fridge.

For the Stewed Prunes in Olorosso Sherry and Vanilla

• Place all ingredients with the reserved vanilla pods in a saucepan over high heat for 20 minutes, until the prunes soften and become syrupy.
• Taste and adjust sweetness and tartness to your liking.

To assemble the cake

• Unroll the cake, spread with cream, more heavily on the cake surface closest to you and sparingly towards the end furthest away.
• Leave a tablespoon of cream.
• Roll the cake away from you gently tucking as you roll.
• Wrap with greaseproof paper and leave to set in the fridge.

To Serve

• Using a knife, shave dark chocolate.
• Smear the remaining cream on the top of the swissroll, sprinkle the shaved chocolate over the top.
• Garnish with the lemon peel and vanilla pods from the stewed prunes.
• Place the prunes and syrup into a small serving bowl.