Preheat the oven to 350 F and line a baking sheet over a square mould.
Beat together butter and sugar until they turn creamy.
Add the sweetened condensed milk, vanilla essence, milk to it and beat again until the mixture turns soft.
Meanwhile, sift the flour with baking soda and baking powder. Now add the dry ingredients to the wet ingredients, mix with a spatula until everything get well mixed.
Pour the cake batter to the prepared mould and bake for 20-25 minutes.
Make a chocolate icing by melting together the chocolate chips, butter, milk and sugar in a microwave safe bowl for 3-4 minutes.
Now add the unsweetened cocoa powder to the icing and mix well.
Cut the cake into square halves and keep the first one aside.
Spread the chocolate icing over one layer of the cake and then top with another layer of the cake.
Now whisk the boiling water to the prepared icing and mix well.
Dip the lamingtons in the chocolate icing and roll them immediately to the desiccated coconut until the lamingtons gets well coated on all sides, roll again in desiccated coconut for a beautiful coating.
Leave them on a wire cooling rack until the chocolate icing gets firms.