Preheat oven to 160°C.
Separate the eggs.
Add oil into the yolks, shake the bowl gentlly to cover the yolks with oil, mix well.
Add in milk gradually, set aside.
Beat egg whites at low speed until foamy.
Add 50% sugar and beat egg whites at low speed until it thickens and becomes glossy.
Add the remaining 50% sugar and beat egg whites at medium until stiff peaks form, set aside.
Add and whisk sifted flour and baking powder into the yolk batter gradually.
Mix until there is no lump.
Gentle fold the egg white meringue into the yolk batter (gently fold in, otherwise you won't get the airy fluffy texture).
Pour the mixture your preferred mould.
Tap to release large air bubbles.
Bake at 160C for 10mins (you might need longer if your cake is thicker, my cake batter was spread to only 1-1.5cm thick).
Once it's cooked, tap to knock hot air inside the cake and let it cool down completely.
Cut the cake into your desired size, mine ones are 8".