Using your Kenwood Chef, beat together egg yolks and castor sugar until light.
Mix cocoa, heated orange juice, orange essence, brandy and oil. Add to the egg-yolk mixture, alternating with the sifted flour, cornflour, baking powder and salt.
Beat egg whites and cream of tartar to form stiff peaks and fold into batter mixture.
Pour into a chiffon cake pan and bake for 50 to 60 minutes, or until cooked through.
Heat cream and add chocolate. Stir until smooth. Refrigerate until cold.
Beat together icing ingredients, except food colouring and decoration, until light.
Add equal drops of red and yellow food colouring to give icing an attractive orange colour.
To assemble Cover cooled cake with three quarters of the orange icing.
Beat the chocolate ganache until light and fill a piping bag. Pipe ganache up and down the sides of the cake. Use remaining orange icing to decorate the top of the cake and around the base and top with the glazed zest and mint leaves.
GLAZED CITRUS ZEST
Heat 150ml water and 50ml castor sugar until sugar has dissolved.
Add zest of two oranges, two satsumas, one lemon and one lime. Boil until syrupy.
Remove zest from syrup and place on a wire rack.
Place in the oven and leave until crisp.
Sprinkle with extra castor sugar as soon as zest comes out of the oven and set aside to cool.