Pre-heat the oven to 150C (keeping the oven at a low temperature for this recipe will ensure an even rise across your sponge cake). Line a large rectangular baking tray with baking paper.
Place your butter in a large bowl, and whisk until a light-yellow colour and fluffier in texture. Add the caster sugar and cream together.
Whisk your eggs in a separate large bowl until light and nearly soft peaks.
Add the eggs to your butter and sugar mixture. Add the vanilla and milk, then mix on a high speed until you have a thin cake batter. (If the mixture looks like it has slightly split, that is fine, it will come together when you add the flour)
Pour in the flour and Roogenic Wattleseeds and mix one final time until you have a beautiful light cake batter.
Pour mixture into your baking tray and try to ensure you get into the corners to ensure a nice rectangle shape after baking (you can even bang the baking tray against the bench to help spread the mixture and eliminate any air bubbles. Bake in the middle of the oven for approximately 30 minutes, or until a cake tester comes out clean.
Once golden brown, remove from the oven and allow to cool on a wire rack (this is very important if you do not allow the lamingtons to cool they will fall apart when tossed in the icing).
Once cool, cut into 6cm squares or desired size.
Sift together the icing sugar and cocoa. Mix with the boiling water and melted butter. Using 2 forks to hold the sponge squares, dip in the chocolate icing and roll in desiccated coconut. Allow to set on a wire rack. This should make 9 Roogenic Wattleseed Lamingtons