Boil the water and switch off the flame. Add the ada and soak for 30 minutes. Check the directions on the package for the cooking timings of the rice ada.
Heat milk in a heavy bottomed pan. When it brings to a boil, reduce the flame to low-medium, add the sugar and let it simmer for 35-40 minutes until it reduces to about one and half cup.
Drain the rice ada, add it to the thick milk, and simmer for 4-5 minutes.
Add crushed cardamom and simmer for a minute. Remove from the flame.
Heat ghee in a pan, add the cashews and when it turns golden brown, add the raisins and fry for 30 seconds. Remove from the flame and add it to the payasam. Serve hot, warm, or chilled.