Chocolate and orange ripple cake

Preheat oven to 180 ºC. Beat butter and sugar together until light. Add eggs a little at a time and beat well. Fold in flour and milk, adding a third of each at a time. Divide mixture in half. Stir orange zest, liqueur and nuts into one half and cocoa powder into the other half.
Place spoonfuls of orange mixture into a greased 22 cm ring cake tin. Place spoonfuls of chocolate mixture into gaps between orange mixture. Using a knife, swirl mixtures together lightly. Bake in the oven for 50-60 minutes, or until cooked through.
Allow to cool in the tin. Loosen edge with a knife. Turn out on to a serving plate, then dust with icing sugar. Makes 1 cake.