How to cook
For the layers, mix everything excluding the yoghurt, baking soda, cocoa and flour. Dissolve the baking soda in the yoghurt and add it to the rest of the mixture, then begin adding the flour in parts.
Divide the resulting mixture in 2, add the cocoa to one of them.
Pour the mixture without the cocoa into an oiled cake form. Pour the mixture with cocoa over it, without stirring.
Bake in a preheated 390°F (200 °C) oven for about 20-25 min. Check with a toothpick to see if it's ready.
For the cream, whip the egg whites to snow and begin adding the sugar, while still stirring. You can add more or less than 1 cup of sugar to the whites, as you prefer.
Once the cake layer is ready, leave it to cool and cut it carefully so you end up with 2 cake layers. Distribute the egg white and sugar cream between them.
Optionally, melt chocolate over the cake and use it to decorate all over.