First wash the colocasia leaves well, remove its stem and middle stem part on the leaves too. Now chopped the leaves as shown below.

Now start boiling the leaves for 5 minutes then drain butter excess water by pouring it on the strainer as shown below in the image.

Now heat a pan, add some mustard oil for frying the prawns. If you have shrimps then add that directly after adding salt and turmeric powder to it. But as I was having tiger prawns so I cut them into pieces first and then added some salt and turmeric powder. Coat them well with the prawns and start frying it. Now keep this fried prawns aside.

Then heat another pan, add some mustard oil. Now add some kalounji to it. When it starts spluttering, add a bay leaf and dried red chilli in it. Then add chopped onion and chopped green chillies too it. Now add little turmeric powder and salt and mix it.

Once the onion is fried properly add the fried prawns in it and mix it. (shown in step 3) Let it fry for about a minute.

Smash the boiled potato a little bit with your hands and add this into the pan. Now combine everything well with the masala. Add little salt and sugar at this point. Keep the flame low, cover the pan and let it cook for 5 minutes. Keep stirring in between.

Open the pan and stir it once again. Let it cook for 5 to 8 minutes more on a low flame. Sprinkle a tsp of mustard oil over it and give it a mix. Switch off the flame. Your kochu shaak is now ready to serve. Serve it hot with some steamed rice. It just tastes heaven. For garnishing, I've topped it with a fried prawn. You can decorate it as per your taste.