Preheat the oven to 180 °C (350 °F).
Spray a 38 x 25 cm baking sheet with non-stick spray and line with wax paper. Spray again.
Beat the egg yolks in a small mixing bowl until thick and light.
Add the icing sugar a spoonful at a time and beat until all the icing sugar has been added.
Beat in the vanilla essence and cocoa.
Beat the egg whites in a clean, fat-free mixing bowl until stiff, but not dry. Carefully fold the egg whites into the cocoa mixture.
Spoon the mixture onto the prepared baking sheet and spread evenly.
Bake for about 15 minutes until done. Sprinkle icing sugar on a clean cloth. Turn the chocolate Swiss roll out on the cloth and carefully remove the wax paper.
Roll the cake and the cloth up together, starting at one of the narrow ends. Allow to cool completely.
Whip the cream and vanilla essence until stiff.
Carefully unroll the Swiss roll and remove the cloth.
Cover the cake with the whipped cream and arrange the mandarin segments on top.
Roll up carefully again and place on a serving platter.
Sift a little icing sugar on top.
Recipe reprinted with permission of You.