Preheat oven to 180°C (160°C fan) and line an 8 x 12-inch baking tray.
Beat the butter and sugar until light and fluffy. Beat in the eggs, then the vanilla.
Add the flour, salt and slowly add milk, mixing until just combined.
Pour into the prepared tray and bake for 30–35 minutes, or until a skewer comes out clean. Cool completely, (chill before cutting if possible)
Cut into 12 large rectangles (or your preferred shape).
Just before coating the lamingtons, whisk together the icing sugar, cocoa, butter and boiling water until smooth. Don’t make the icing too early, as it will begin to thicken as it cools.
Dip each piece into the icing, allowing the excess to drip off, then immediately coat in desiccated coconut. I found using my hands worked much better than a fork, as the cakes were less likely to break.
Place on a wire rack until the icing has set.
