Wash the yam thoroughly to remove all dirt, peel the skin and chop it into small pieces.
Boil the yam pieces in sufficient water.
Grind it to a smooth paste using a mixie. Also coarsely grind it for more texture
Melt jaggery in little water and strain it to remove any impurities.
Soak the sago for 1/2 an hour, boil it till it becomes transparent and keep aside
Take a heavy bottom pan. Add the jaggery syrup, boiled sago and yam paste to this.
Add the coconut milk and boil the mixture.
Add more water or coconut milk and boil it to bring it to your desired consistency.
Add the crushed cardamom pods.
Heat ghee and roast the cashews and raisins in a small pan. And add it to payasam.
Switch off flame and cover it.
Let it rest for a few minutes before serving.