Foolproof Sponge Cake

Foolproof Sponge Cake
From Baking Illustrated

1/2 cup plain cake flour
1/4 cup unbleached all-purpose flour
1 tsp baking powder
1/4 tsp salt
3 tbsp milk
2 tbsp unsalted butter
1/2 tsp vanilla extract
5 large eggs, at room temperature
3/4 cup sugar

1. • Preheat oven to 350F.
   • Grease pan and cover bottom with parchment or waxed paper.
   • Whisk the flours, baking powder and salt into medium bowl.
   • Heat milk and butter in a small saucepan over low heat until the butter melts. Remove from the heat and add vanilla. Cover and keep warm.
2. • Separate 3 eggs, placing whites in the bowl of standing mixer, reserving the 3 yolks plus the remaining 2 whole eggs in another mixing bowl.
   • Beat the 3 whites at low speed until foamy.
   • Increase the mixer speed to medium and gradually add 6 tbsp of the sugar; continue to beat the whites to soft, moist peaks. (Do not overbeat.)
   • Transfer the egg whites to a large bowl and add the whole-egg mixture to the mixer bowl.
3. • Beat the whole-egg mixture with the remaining 6 tbsp sugar.
   • Beat at medium-high speed until the eggs are very thick and pale yellow color, about 5 minutes. Add the beaten eggs to the whites.
4. • Sprinkle the flour mixture over the beaten eggs and whites; fold very gently 12 times with a large rubber spatula.
   • Make a well in one side the batter and pour the milk mixture into the bowl.
   • Continue folding until the batter shows no trace of flour and the whites and whole eggs are evenly mixed, about 8 additional strokes.
5. • Immediately pour the batter into the prepared cake pans; bake until the cake tops are light brown and feel firm and spring back when touched, about 16 minutes for 9-inch cake pans and 20 minutes for 8-inch cake pans.
6. • Immediately run a knife around the pan perimeters to loosen the cakes.
   • Place one pan on a towel and cover the pan with a large plate.
   • Using the towel to protect your hands and catch the cake, invert the pan and remove the pan from the cake.
   • Peel off the parchment.
   • Reinvert the cake from the plate onto the rack.
   • Repeat with the remaining cake. Cool cake layers to room temp before proceeding.

Note* I made this cake at someone else's house. This was the only cake pan they had. It still turned out perfectly.