Start by lining your baking tin with a grease partchment paper and set aside. C

Crack the 4 egg and beat dem in a large bowl. Beat dem until a litfy foaming about 1 minutes.

Add sugar give it good whisk until nice and thick. Slowly add oil while whisking. Whisked the mixture until all oil is mixed throughly.. Finally add the milk and vanilla extract.

Sift the flour and add to the egg mixture. Give it good mix until no flour is visible make sure there is no lumps. Get new bowl decided the mixture in to 2 equal parts adding to 1 bowl a cocoa powder and whisk together to combined.

Using a ladle scoop the white mixture and pour in to the center of the prepared baking tin, using anoda different ladle at the same size scoop the chocolate mixture and pour at the white mixture and allow to separate itself, repeat the procedure bit by bit until u have finished. The trick is to aim for the center and allow to separate evenly.

Place in a preheated oven @ 180 degress/350f.bake until tookpick is inserted and come out clean.