Drive egg whites into a deep plate and beat until fluffy.
Mix the yolks with sugar and beat well.
Add half the whipped whites and sifted flour to the yolks. Mix everything well.
Add the rest of the proteins and mix gently.
Pour the dough into a baking dish and place in an oven preheated to 180 degrees for 30-40 minutes. Check the readiness with a wooden skewer; when piercing the biscuit, it should remain dry.