Break the chocolate into small pieces and melt suspended over a pan of boiling water.
Add the cream to a bowl and whip with a hand mixer. Pour in the melted chocolate from Step 1.
Mix the chocolate and cream together briskly with a whisk.
Keep whisking until fully mixed.
Make a meringue by whisking together the egg whites with a hand mixer.
In a separate bowl, combine the egg yolks and sugar with the sifted flour, cornstarch and cocoa. Add 1/3 of the meringue and mix until smooth.
Add the rest of the meringue in 2 more batches and mix in.
Line a baking tray with baking paper and pour the mixture from Step 7 in from a height to eliminate any excess air. Bake for 10 minutes in an oven preheated to 180℃.
Once baked, wrap tightly in cling film whilst still warm. (Once cooled, peel away the wrap to get rid of the burnt surface).
Lay the sponge on top of some baking paper and spread the cream from Step 4 evenly over the top. Heap the cream up more on the side closest you so that the middle of the rolled cake is more cream-filled.
Roll the sponge away from you gently. Then wrap with cling film and chill in the refrigerator to finish.
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Story Behind this Recipe
I wanted to make a swiss roll with a double punch of chocolate.
For Step 2, start mixing the chocolate into the cream as soon as it's poured in so that it doesn't harden. For Step 6, by pouring in just 1/3 of the meringue to begin with, the mixture will gradually become nice and smooth. For Step 10, make sure the better looking side of the sponge is on the bottom.