Beat oil, sugar and egg, and add vanilla essence to the mixture.
Sieve flour and baking powder (thrice) and add to the mixture.
Add milk as well.
Separate 1/3 quantity of the mixture and add drinking chocolate to it.
Grease the pan and sprinkle flour.
Pour the mixture alternately to form different layers.
Bake in a pre-heated oven for 40 to 45 minutes.
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