Stir until you get a homogeneous mixture.
Divide it into 2 piles, add the cocoa to one of them.
In an oiled tray, pour 1 tbsp of each mixture, alternating between 1 tbsp of the white and 1 tbsp of the brown one.
Continue in this manner until you run out of mixtures.
Bake the cake in a preheated 320°F (160 °C) oven.