Preheat oven to 160 degrees Celsius. Grease a 20cm, deep baking pan, with some vegetable oil. Line the bottom of the pan with baking pan
Beat the butter and sugar, using an electric mixer, until light and creamy, takes about 4 minutes
Separate the egg yolks and egg whites. Add the egg yolks, one at a time and beat until combined
Add the vanilla essence and mix well. Sift the flour and baking powder together and add half to the butter mixture together with half the milk. Beat just a few seconds and add the other half. Beat until combined. Do not over mix. Pour the batter into the lined baking pan
Whisk the egg whites until soft peaks form. Add little bits of castor sugar at a time and beat until stiff peaks form. I used an electric hand mixer throughout the process and I used speed 2 on my Kenwood mixer. See Note 2&3 below
Fold the coconut into the eggs whites. Spread it over the cake batter and bake for 1 hour, in the middle rack or until a toothpick inserted comes out clean
Allow the cake to cool for about 10 minutes before turning it onto a cooling rack. Cut and serve once completely cool