Chocolate Passover Sponge Cake - cooking recipe

Ingredients

cooking spray
1/4 cup matzo cake meal, sifted
3/4 cup potato starch, sifted
10 eggs, separated
1 cup white sugar
1/2 cup unsweetened cocoa powder
1/2 cup white sugar
3 tablespoons cold strong coffee
1/4 cup chopped walnuts, or to taste (optional)

Preparation

Preheat oven to 325 degrees F (165 degrees C).
Spray a 10-inch tube pan with cooking spray.
Sift matzo cake meal with potato starch into a bowl; set aside.
Place egg yolks into a large mixing bowl and beat with an electric mixer on medium speed until light, about 3 minutes.
Slowly beat 1 cup sugar into the egg yolks; continue beating until mixture is thick and pale, about 5 more minutes. Beat cocoa powder into the egg yolk mixture until thoroughly combined.
Beat egg whites with an electric mixer fitted with clean beaters in a separate bowl until foamy. Gradually beat in 1/2 cup sugar and continue to beat until egg whites hold stiff peaks.
Lightly stir matzo cake meal mixture and coffee into egg yolk-cocoa mixture.
Gently fold 1/3 of the egg whites into the batter, retaining as much volume as possible. Fold in remaining egg whites, mixing just until no white streaks remain. Gently mix in chopped walnuts.
Spoon the batter evenly into the prepared tube pan.
Bake in the preheated oven until top of cake shows small cracks and springs back when lightly pressed, about 45 minutes.
Run a knife around the sides of cake to loosen from the pan. Invert cake onto a wire rack to cool.