Dissolve the sugar in water and oil.
Combine the sifted flour with the baking powder and unsweetened cocoa powder, and mix the mixture with a whisk until smooth.
Beat the egg whites until stiff peaks form, then gently fold them into the batter.
Pour the mixture into a baking dish that has been buttered and floured, and bake in a conventional oven at 180° C for 40–50 minutes.
Let the cake cool, then dust it with powdered sugar before serving.
This cocoa egg-white cake was created to use up the leftover egg whites from previous recipes.
It’s a soft, delicious cake, and the egg whites give it an indescribable lightness. You can easily customize it with chocolate chips or fruit of your choice, or slice it and fill it with Nutella, milk cream, or apricot, strawberry, raspberry, fig, or pear jam.