Ingredients
1 cup flour
4 Tbsps cocoa powder
1 cup powdered sugar
1 tsp baking powder
1/2 tsp soda
1 cup milk
2 tbsps vinegar
1 egg
1 Tbsp melted Butter
1 tsp essence
a pinch salt

Method
1) Mix milk & vinegar & keep for 15 mins to curdle ( This gives you one cup of sour milk).
2) Mix the flour, baking powder, cocoa powder, soda & salt & sieve twice. Set aside.
3) Beat the egg & powdered sugar together until creamy. Add the vanilla essence to this. Add the melted butter to the egg sugar mixture & mix thoroughly.
4) Add the sieved flour mixture, alternating with sour milk to make a smooth batter. Pour this batter in a greased dish. Cover the dish with butter paper & steam on moderate heat for 45 mins in a steamer or bake in a moderate oven (180  ^oC / 350 ^o F) for 30 - 40 mins.

( Source Laxmi Nair - Asian Age