Line a 10” square pan with non-stick baking paper/
Preheat the oven to 325 degrees
In a large bowl, pour in the melted butter, add in the sugar, sour cream, vanilla extract and oil. Beat for a minute or until smooth.
Add in the eggs, one at a time
Sift in the flour and baking powder and stir well.
Spoon the batter into the lined pan.
Cover the top with foil and bake for about one hour. Remove the foil after 40 minutes. Use a toothpick in the middle it should come out clean when it is done.
Cool the cake in the pan, covering the top with plastic wrap or foil as it cools to keep it moist.
To make the coating:
Finely chop the chocolate and set aside.
In a saucepan, whisk together the cocoa, sugar and milk and bring to a boil.
Remove it from the heat and stir in the chocolate, set aside until it is warm but not too hot to handle.
Slice the cake in squares
Pour the warm syrup into a bowl deep enough to submerge the cake squares in it.
Have a tray ready with the coconut.
Using your fingers, dip the lamingtons into the syrup, then roll them in the coconut.
Allow the chocolate to set for a few hours before serving.
They store well in an airtight container.