Make slurry of corn flour and coco powder by mixing some milk so that there should be no lumps.

Now boil milk.

Add slurry to warm milk and take a boil to the milk.

Now add sugar to mixture.

Add some crushed chocolate in the mixture and boil for 4 to 5 minutes.

Now take this mixture to room temperature and put it in freeze for 2 hours.

Now cold coco is ready to serve. Serve this chilled cold coco with some crushed chocolate.