Other side take butter in a bowl.add sugar in it and mix it well. Whisk it for 5 minutes so that sugar mix with butter properly..

Add flour mixture in it gradually. Stir it constantly while mixing...so that lumps can not be produced.

Then take 2 to 3tablespoon cold milk in a bowl and add coca powder in it.Mix it properly. Add this mixture to flour mix and stir it well to give a better chocolate flavour.

Add some plain milk gradually in to better to make pour like consistency...Better should not be thin.

Now take a cake tin and grease it with butter. Sprinkle 1 tsp maida in the tin and tap it to spread it over all.Pour better gradually and tap the cake tin to make layer symmetrical.

Other side take steamer or cooker on the flame and fill it's bottom with the sand.Preheat it for 10 minutes. Then put stand and Aluminium cake tin over it. Close the lid of cooker with out whistle. And make the flame full for 10 minutes. Cake started to cook and back.

After 10 -15 min cake started to swell...then keep it on the medium flame for another 15 min..Mostly the cake would bake.Then with the knife check it whether it is cooked or not. If it is baked knife will remain clean.Otherwise cake would stick on the knife during checking.