Take a bowl and add 1 cup curd in it.
Add 1 tsp baking soda and 1.5 tsp baking powder.
Mix well.
Leave for 5 minutes and you will find a frothy curd.
Add 1/2 cup oil, 1/2 cup milk, 3/4 cup sugar and 1 tsp vanilla essence.
Mix well.
Put a sieve on the bowl.
Add 2 cup whole wheat flour and pinch of salt.
Sift the flour into the bowl.
Mix into a batter by using cut and fold method.
Take 2 tbsp of batter and add into a small bowl carrying 2 tbsp cocoa powder.
Mix well.
To make it a thick but flowing consistency of cocoa batter, add bit of the milk. Keep aside.
Pour that white batter in a large and wide pan lined with greased butter paper. We have used 8×12 inches pan.
Now swirl the cocoa batter roughly over the white batter using a spoon.
Take a toothpick and swirl it through the batter, making rounded vertical zig-zags from one side of the pan to the other. For better understanding, watch the video attached to this post.
Bake in a pre-heated oven @160°C in the middle rack of the oven for 20-25 minutes.
Check using the toothpick and if it comes out clean, its a sign that cake is properly baked.
Let it cool down completely.
Serve by slicing the cake into pieces of desired size.