The recipe for this easy sponge cakes with only 5 ingredients, gives airy, crunchy and slightly sweet cookies. The cookies will melt on your tongue. Delicious to the last bite.
Preheat oven to 350 degrees Fahrenheit / 180 degrees Celsius.
Line a baking plate with parchment paper.
Separate the eggs.
Place the egg whites in a bowl and egg yolks in another bowl.
Mix the egg whites with a mixer.
Stir tablespoon by tablespoon ⅔ of the white sugar into the egg whites, while you keep mixing.
In the bowl of the egg yolks, add the lemon zest and the rest of the sugar.
Mix with a whisk until the egg yolks airy and light yellow in color.
Add ⅓ of the egg whites to the egg yolks and gently combine with a spatula.
Sift the flour and cornstarch over the egg-yellow bowl and gently mix into the egg mixture (small lumps aren't a problem).
Finally, add the rest of the egg whites to the batter and gently whisk in with a spatula.
Make 10 piles of batter on the parchment paper. Keep sufficient distance between the cookies because they will rise a bit in the oven (use when necessary two trays).
Bake the sponge cookies for 20 minutes and then remove them from the oven.
Let them cool on a wire rack.
NOTES
The recipe asks for stiff egg whites. To get them you must make sure that your bowl is fat-free. Therefore wash it beforehand thoroughly with hot water and detergent. This also applies to the hooks for the mixer.
To get a smooth batter you first add just a little egg white and gently mix it through. This way you let the batter get used to the airy egg white. Then you can add the rest of the egg white carefully to the batter and gently mix it with a spatula. That way the batter becomes airy.
Add cornstarch to the batter so it stabilizes and won't collapse. That way your sponge cookies will stay fluffy.