Step 1

Heat the oven to 170C/Gas Whisk the egg whites until stiff, gradually add the caster sugar and whisk until thick. Sift the cocoa powder over the top, add the vinegar and fold in.

Step 2

Spoon the meringue into the lined tin and level the surface. Bake in the centre of the oven for 50 mins, or until just firm to the touch. Remove from the oven and cool for 5 mins, then turn out onto a clean tea towel and peel away the lining paper. Allow to cool completely.

Step 3

For the Baileys cream, whisk the mascarpone, Baileys and icing sugar until thick. Warm the chocolate spread in the microwave for 10 secs, until runny.

Step 4

To assemble, spread the Baileys cream mixture over the sponge and drizzle over the chocolate spread, reserving a little. Remove as much of the outside of the clementine sections as possible, so that you are left with just the flesh. Reserve a few. Arrange the clementines on top of the cream and use the tea towel to help you roll up the roulade lengthways.

Step 5

Dust with cocoa powder and half-dip the physalis and reserved clementines in the remaining chocolate spread and arrange on top, along with sparklers.