In a dish mix the dry ingredients (sugar, flour, soda, cocoa). Add the egg yolks, yogurt and oil. Stir.

In a separate bowl whisk the whites with a spoon of sugar, pour in the batter, bring to a homogeneous condition. The dough will be liquid, but not to worry, it is baked through.

Pour into form and bake for 20 minutes at 190 degrees. I was determined intuitively and by means of a match. Due to the finicky oven pitch in two forms (~25 cm in diameter), so the cake turned out quite flat. If you use one form, then, presumably, it will come out puffier. Brew tea and eats his creation :-)