Separate the egg whites and yolks into two bowls.
Whisk the egg yolks with milk and vanilla extract until combined.
In a separate bowl, mix flour, cornstarch, baking powder, and salt.
Gradually add the dry ingredients to the egg yolk mixture and stir until smooth.
In another bowl, beat the egg whites until soft peaks form.
Gradually add sugar while continuing to beat until stiff peaks form.
Gently fold the egg whites into the yolk mixture in three parts.
Heat a non-stick skillet over low heat and lightly grease it with butter.
Pour batter onto the skillet and cover with a lid.
Cook for about 4-5 minutes on each side until golden brown and fluffy.