Wash, peel and cut the mango into medium size pieces.
Put the mango pieces, turmeric and half cup of water in a pressure cooker.
Cook till 3 or 4 whistles. Turn off the flame and wait until the pressure go off.
Then remove the mango pieces from the cooker. When it cools down, mash the mango pieces with fingers or masher.
Put the mango pulp, salt, rasam powder, grated jaggery, green chillies, chopped coriander leaves and 2 - 3 cups water in a heavy bottomed pan.
Let it cook for 10 to 15 minutes on a medium flame and remove from the heat. Heat half teaspoon of oil in a pan and add mustard seeds, cumin seeds.
When they start to splutter add hing and red chilli and stir for few seconds.
Turn off the flame and pour over the mango rasam. Mix well and serve hot with steamed rice and sun dried chillies.