Grind together coconut, jeera, green chilli and turmeric powder with 1 tbsp water to a smooth paste. Roast the moong dal in a pressure cooker for 4-5 mins on low flame, till you get the roasted smell.
Add 3 cups water to the roasted dal. Mix well. Cover the cooker and pressure cook for 8-10 whistles on full flame. Switch off the gas and let the pressure drops naturally.
Mash the cooked dal using a wooden spoon or you can just run it in a food processor or blender for a few seconds.
Add ground paste, salt and 1/2 - 1 cup water to the mashed dal. Let it cook on low flame for 5-7 mins. Remove from heat.
Heat oil/ghee in another pan and splutter mustard seeds. Add small onion, curry leaves and red chilli. Fry till small onion becomes golden brown. Pour over cooked dal. Serve with rice and pappad, wait... don't start eating... drizzle some ghee on the curry, now you are ready to eat :)
Notes
You can also cook the dal using pressure cooker. Cook on high flame for 5-6 whistles. keep it closed for 10-15 mins and open the cooker. I recommend using ghee for this recipe.