In a large bowl, mix together the oil, milk, and egg yolks
Sift in cake flour and corn starch. Mix until combined and then set aside.
In another large bowl, add in the egg whites and cream of tartar. Mix until frothy then add in the sugar 1/3 at a time until you reach stiff peaks
Add in 1/3 of the egg whites at a time into the egg yolk batter. Gently fold until everything is combined
Transfer batter into a muffin tin
Bake at 110C/230F for 40 minutes and then 160C/320F for 5-10 minutes until golden brown