1.      Preheat oven to 170^oC.  Grease and line a 22cm x 32cm baking tin.  Using an electric beater, cream butter and sugar until light and fluffy.  Beat in eggs one at a time.  Add vanilla essence into creamed mixture, sift over flour and baking powder and mix in with milk until well combined.  It is best to stir in the flour and milk rather than fold in otherwise the cake will be too fluffy, making it harder to cut and dip.

2.      Spread mixture evenly in tin and bake 18-20 minutes until lightly browned and springy to the touch.  Cool in tin for 5 minutes before turning out on to a wire rack to cool completely.  Trim edges and cut cake into 40 pieces (5 rows x 8 rows).

3.      To make icing, place milk, chocolate, butter and cocoa in a saucepan and whisk over heat until smooth. Remove from heat and whisk in icing sugar. Using a fork, dip cake squares into icing and drain.  The icing needs to be just thick enough to cat the cake evenly.  A little boiling water can be added if necessary but try a test square of sponge first; if the icing is too runny it will not set.

4.      To toast coconut, spread it in a shallow oven pan and place in a moderate oven for a few minutes until lightly browned and fragrant.  Watch carefully and stir often as coconut burns quickly.  For textural interest, coat the lamingtons with a mix of desiccated and threat coconut.

5.      Place coconut in shallow container.  Toss squares in coconut to coat.  Place on a wire rack to set (about 20 minutes).  Place a sheet of baking paper underneath the rack to catch the drips; it makes cleaning up easier.

6.      Lamingtons will keep well for 1-2 days and leftovers can be frozen.