Beat the egg whites and yolks separately. Then mix them, add the sugar, milk, oil and vanilla.
Once mixed, add in the flour and baking powder. Set aside 5-6 tbsp of the mixture.
Pour the rest of it into a floured and greased cake form.
To the set aside part add the cocoa. Then pour it lengthwise over the other cooled mixture.
Swirl your knife around in circular motions over it to make stripes. Bake at 302°F (150 °C) until ready.