Castella Sponge Cake

INGREDIENTS
2 Egg yolks
25g Melted unsalted butter
45g Milk
2g Vanilla extract
30g All-purpose flour
50g Tapioaca starch
2 Egg whites
30g Sugar

INSTRUCTIONS
Mix egg yolks, add melted butter, and mix.
Add the next milk and vanilla extract and mix.
Sift flour and tapioca starch, mix and let stand for a while.
Divide the egg white into sugar 2 times and make a hard meringue.
Add 1/3 of the meringue to the egg mixture and mix, then transfer to the bowl where the meringue remains and mix.
Put a parchment paper cup into the muffin mold, fill it with batter, and bake at 180 degrees for 20 minutes. (Preheat 200 degrees)