Chocolate Sponge Cake - PCOS-Friendly Recipe

Preheat oven to 400 °F. Line the bottom of a 13x9x2" metal baking pan with parchment paper. Butter paper and sides of pan; dust with cocoa powder, tapping out excess. Sift flour and remaining 1/4 cup cocoa powder through a fine-mesh sieve into a small bowl. Repeat sifting 2 more times. Set flour mixture aside. Crack 2 eggs into a large deep bowl. Separate remaining 2 eggs, adding yolks to bowl with whole eggs and placing whites in a medium deep bowl. Set whites aside.

Using an electric mixer, beat whole eggs and yolks on low speed for 1 minute. Increase speed to medium; gradually add 1/2 cup sugar. Beat until mixture is thick and pale, about 3 minutes. Beat in vanilla.

Using clean, dry beaters, beat egg whites until foamy. Sprinkle 1 teaspoon sugar over. Continue to beat until soft peaks form, about 1 minute. Sprinkle remaining 5 teaspoons sugar over and beat until meringue is thick and glossy, about 30 seconds.

Using a rubber spatula, fold half of meringue into egg mixture. Sift half of dry ingredients over batter and fold until just blended. Repeat with remaining meringue and dry ingredients.

Scrape batter into prepared pan, spreading evenly to edges. Bake until cake springs back when pressed gently with your fingertips, 10-12 minutes.

Let cake cool in pan on a wire rack. Run a knife around sides of pan to release cake.

Place a cutting board on top of pan. Invert cake onto board; remove pan. Carefully peel away parchment. Using a serrated knife, trim edges to create an even layer.