Method

• 1.
  Preheat oven to 200°C/180°C fan-forced. Grease a 38cm x 26cm baking tray and line with baking paper.
• 2.
  In a stand mixer fitted with the whisk attachment, whisk egg yolks and caster sugar until thick and pale. Sift over the cocoa and flour and stir until combined, then add chocolate and milk and stir until smooth and combined.
• 3.
  In the clean bowl of a stand mixer fitted with a clean whisk attachment, whisk egg whites to soft peaks. Fold one-quarter of the egg white into the chocolate mixture until combined, to loosen the texture, then carefully fold through remaining egg white (do not overmix).
• 4.
  Pour sponge mixture into prepared pan and smooth to edges. Bake for 15 minutes, or until sponge springs back when gently pressed.
• 5.
  While the sponge is still warm from the oven, lightly sprinkle a clean tea towel with extra sugar, then invert sponge onto tea towel. Remove tray and baking paper. Sprinkle sponge with a little extra sugar. Starting from one short side, roll up sponge in tea towel and set aside to cool completely.
• 6.
  For the chantilly, whisk all ingredients in a large bowl to soft peaks. Chill until ready to assemble.
• 7.
  To assemble, gently unroll sponge and spread with chantilly, making sure to spread out right to the edges. Roll sponge back up and transfer to a wire rack set over a baking tray (see recipe notes).
• 8.
  For the glaze, stir the sugar in a small saucepan over medium-high heat until sugar dissolves and turns a dark caramel colour. Remove from heat and carefully add ⅓ cup (60ml) warm water (caramel will spit). Add cream, return to medium-high heat and bring back to the boil, whisking until smooth. Add chocolate and remove from the heat. Stand for 5 minutes, then whisk until smooth, setting aside to cool and thicken slightly.
• 9.
  To glaze roulade, starting at one end of the roulade and moving along its length, slowly pour the glaze over the roulade (see recipe notes). Chill in the fridge for 10 minutes, for glaze to set.
• 10.
  Serve cut into slices.