Method 

Preheat the oven to 180oC. Line a 32cm Swiss roll tray with parchment paper. 

In a bowl or your stand mixer whisk the eggs and caster sugar for 3-4 minutes until thickened and they become nice and pale and fluffy. 

Add the flour, baking powder, and cocoa powder to a bowl and sieve into the egg and sugar mixture. Fold with a spatula until there are now pockets of flour left. 

Gently spoon it onto the lined tray and smooth it out making sure it fills the tin evenly. 

Bake for 15 mins until it puffs up and becomes springy to touch. 

Allow to cool for 1 minute and then gently remove from the tray. Run a rolling pin over the sponge gently to flatten it. Roll up both ends using the parchment as your guide and allow them to meet in the middle. Allow the sponge to cool. 

While it’s cooling make the filling by beating together with an electric beater the butter and icing sugar until it goes a nice pale white colour. 

Once cooled slice through with a knife the middle of the sponge where the two rolls meet and unravel them. 

Spread on the filling evenly with an offset spatula and then roll them back up with the filling inside. Slice them into 6 portions and place them onto a wire rack with a tray underneath. 

Melt both the chocolates separately and then firstly spoon over the dark chocolate covering the mini rolls all over. Finally, drizzle the white chocolate over in a zig-zag motion to decorate. 

Place into the fridge to harden before tucking into your delicious mini rolls. Enjoy.