Wash and clean the fish head properly and pat it dry.
Rub 1/2 tsp of turmeric powder and little bit of salt on the fish head and keep aside.
Heat the oil in a kadai or a frying pan and when the oil is hot, fry the fish head. Keep the heat at medium so that the fish head doesn't burn but cooks from inside. It takes about 15 minutes for the fish head to fry properly. Of course the time taken depends on the size of the fish head.
When the head is fried, use a slotted spoon to take it out of the pan.
Now dry roast the moong dal till it gives fragrance. Do not burn it. Just lightly dry roast it. Then wash the roasted moong dal and drain the water.
In a pressure cooker, add 2 1/2 cups of water, 1/2 tsp of turmeric powder, some salt and the moong dal. Pressure cook for one whistle or 10 minutes or until the dal is cooked.
In the frying pan where the fish head was fried, use the same oil to temper the spices. First add the bay leaf, cumin seeds and then the cardamon and cloves. Once they start to splutter, add the onions and fry them.
While the onions are frying, add ginger and garlic paste. In another couple of minutes, add the chopped tomatoes and the cumin powder, coriander powder and red chili powder.
Fry the masala till the raw smell goes off and oil starts to release from the side.
Then add the dal from the pressure cooker. Add some more water to reach the desired consistency.
Break the fish head into 4 or five parts and add to the boiling dal. Let it continue boiling for 5 minutes so that the fish head becomes soft from within.
Check the seasoning and add more salt if required. Add the sugar to balance the flavour.
Drizzle some ghee and add some split green chilies and turn off the heat.
Serve the dal with some steamed rice.