• Preheat the oven to 180°c / gas 4.
• Line a 12" x 8" rectangular tin with baking paper.
• In a large mixing bowl, add the flour, cornflour, margarine, caster sugar, vanilla extract, eggs and 125 ml of milk in a bowl. With an electric whisk, mix until smooth.
• Pour the batter into a tin and bake for 34-40mins or until the skewer inserted in the centre comes out clean. Turn out onto a wire rack and leave to cool.
• Cut the cake into bite size squares and place in the fridge for 30mins.

To make the icing

• Sift the icing sugar and cocoa powder into a bowl.
• Put the margarine and milk in a small saucepan and cook over a low heat for 5mins or until the margarine has melted. Pour over the cocoa mixture and stir until smooth.
• Put the coconut in a bowl.
• Using a fork, dip a cube of cake in the icing, then roll in the coconut to coat all over.
• Place on a wire rack to set. Repeat with the remaining cubes of cake until all are coated.