Line a 30 x 40cm baking tray with baking paper. Step 6Lay a clean sheet of baking paper on a work surface and sprinkle lightly with caster sugar to help prevent sticking. Step 8For the Chantilly cream, put the cream, vanilla seeds and sugar into the cleaned bowl of the stand mixer and beat until the mixture holds firm peaks. Step 9Unroll the sponge and then spread the Chantilly cream evenly over it. Slice and serve with more of the Chantilly cream on the side if desired, decorated with mint leaves if you like.