Preheat and line the tray

• Preheat the oven to 180 °C.
• Line the baking tray with baking paper and lightly grease it.

Make the sponge batter

• Whisk the egg yolks with half of the caster sugar until pale and thick.
• Stir in the warm milk, vegetable oil and vanilla extract.
• Sift in the flour, cocoa powder, baking powder and salt, then fold until just combined.

Whip the egg whites

• Whisk the egg whites to soft peaks, then add the remaining caster sugar and whisk to stiff, glossy peaks.
• Fold the meringue into the batter in three additions, keeping as much air as possible.

Pipe the Totally Spies design

• Divide a small amount of batter into three bowls and colour one red, one green and one yellow.
• Spoon each colour into a piping bag and pipe the design onto the lined tray.
• Freeze the tray for a few minutes so the design sets.

Bake the sponge

• Spread the remaining batter evenly over the chilled design.
• Bake until the sponge springs back when touched.

Roll the sponge

• Turn the warm sponge out onto a sheet of baking paper dusted with icing sugar.
• Peel off the lining paper, then roll the sponge up with the paper and leave to cool completely.

Whip the cream filling

• Whip the cold double cream with the icing sugar to firm peaks.

Fill and roll

• Unroll the cooled sponge and spread the whipped cream over it, keeping a border at the edges.
• Roll the sponge back up tightly and chill until ready to serve.

Serve

• Trim the ends and slice the roll to reveal the coloured design.