Preheat the oven to 180°C. Line a 28 x 19 x 4 cm lamington tin.

To make the cake, cream the butter and sugar until the sugar is dissolved. Add the eggs one at a time, beating after each addition. Gradually add the flour, alternating with the milk or orange juice. Mix together well, then pour the mixture evenly into the prepared tin. Bake for 30 minutes, or until a skewer inserted into the cake comes out clean. Allow the cake to cool completely.

Cut the cake into 4 cm squares, trimming the edges if necessary.

Mix the icing sugar and cocoa together in a bowl. Put the butter into the hot water to melt, and mix into the icing sugar mixture until thick and smooth. Drop the cake squares into the chocolate, ensuring the cake is fully covered, then remove very quickly. Drain the cake on a wire rack for a few seconds. Using a large cooking fork, roll in the coconut.