How to make
Beat the eggs with the sugar and successively add the milk and oil, while constantly whipping. Separately, sift the flour with the baking powder and vanilla and while stirring, add it to the egg mixture. Stir until everything is homogenized.
Divide the mixture into 2 equal parts. Mix one with the melted chocolate or cocoa. Grease and flour a round baking dish. Put 3-4 tablespoons of the light mixture in the center of it.
Then pour over 3-4 tablespoons of the dark mixture in the middle of the white. Continue in this fashion until out of products.
Put the zebra cake to bake in a preheated 360°F (180 °C) oven until done, checking its readiness with a toothpick.
