Whoever thought up this technique was (is?) a genius in his or her own way. Such a simple thing to do, with such spectacular results (especially if done perfectly) - no fiddly procedures, no cutting cakes into shapes, or glueing them with icing or marzipan to construct edifices. Just two batters used alternately. Absolute genius, I tell you.
My cousin Hema and I made this cake - or rather, Hema made it under instructions. Normally I shy away from baking cakes that use more than two eggs - maximum 3 - but this time as I was instructing, it seemed better to follow the recipe exactly instead of improvising. (She can learn improvisation by herself!)
As it turned out, we should have gone with our instinct and "loosened" the chocolate batter which had become thicker than the plain one by addition of cocoa powder. Because we didnt do that in the first place, the first few layers of chocolate didnt fall easily off the spoon and didnt quite make it to the centre of the cake pan.

Oh well... live and learn. (The recipe below has the correct revised measurements.)
Despite our initial hiccup, the inside of the cake looked spectacular when cut.

It had risen rather a lot on one side while baking - probably because the batter was not mixed quite right? - and I surreptitiously pushed it down (carefully!) with the heel of my hand when nobody was looking. Not too much and not too hard, though, because I didnt want to ruin it totally!
All in all, this is a nice cake and excellent for impressing your guests and making them think you're a baking genius!

Previous recipes baked with Hema: Peanut butter cookies, Cashew vanilla cookies, Cranberry orange cookies
Edited to add: Thanks, Divya, for pointing out that I'd said 1/2 tbsp cocoa powder, instead of 1/2 cup! 1/2 tbsp would have done no good at all! Thanks for being so observant! (Recipe has been updated) :)
Recipe for: Tiger cake

Ingredients:
4 eggs
1 cup sugar
1 cup milk
1 cup oil
1 tsp vanilla extract
2 cups plain flour
2 tsp baking powder
1/4 tsp salt
1/2 cup dark cocoa powder
Milk as required
Method:
1. In a large mixing bowl, combine eggs and sugar until creamy and light in colour.

2. Add milk and oil and continue beating till well blended.
3. Add vanilla. Gradually add flour and then beat until the batter is smooth.
4. Divide mixture into 2 equal portions. Keep one portion plain.
5. Add cocoa powder to the other and mix well. Add enough milk to thin out the batter to the consistency of the plain portion.

6. Preheat oven to 180C. Scoop a ladle of plain batter into the middle of the baking pan.
7. Then scoop a ladle of the cocoa batter and pour it in the centre on top of the plain batter. Continue this way until the batters are finished. The more you "layer" them, the more stripes you will get in the finished cake.

Do NOT spread the batter or tilt the pan to distribute the mixture.
8. Bake for 40 minutes or till the cake tests done.
