Preheat oven to 180 degrees Celsius fan-forced. Grease a 22cm fluted ring pan.
Using an electric mixer, beat butter, sugar, eggs, flour, cocoa, bicarbonate of soda and milk on low speed for 1 minute or until just combined.
Increase speed to high. Beat for 2 minutes or until thick and creamy.
Spoon mixture into a pan. Smooth top. Bake for 45 to 50 minutes or until a skewer inserted in the centre comes out clean.
Remove from oven. Stand cake in pan for 10 minutes after being removed from oven. Then turn out onto a wire rack to cool.
Place cake on a plate. Dust with cocoa and serve. NOTE : Optional to add white icing sugar.