After 15 minutes drain the water and grind the rice along with the coconut into a fine paste.
You can add little water while grinding.
In a heavy bottomed pan add the ground paste and add half cup of water. Keep in a low flame. Cook this for 7-10 minutes in a low flame so that the rice will get cooked.
Boil the jaggery with 1/4 cup of water. Filter this if you have any impurities.
Let this jaggery water boil for 2 minutes . Add this to the rice coconut paste. Add little water to adjust the consistency. Do not add more. the payasam will be thick only. Add the cardamom powder.
Switch off the flame. Roast the cashew nuts in ghee and add to this.
Payasam is ready for neivedhyam.
Video
Notes
1. If you want you can add milk to the payasam in the last.2. If adding so ensure both the milk and the jaggery mixture is completely cool. Else the milk will curdle. 3. After adding milk do not reheat. 4. Arisi thengai payasam tends to thicken after it is cool.