Heat oil or ghee in a large pan over medium heat. Add mustard seeds and let them crackle to release their aromatic oils.
Add chana dal, urad dal, and cashew halves. Stir constantly until they turn light golden brown and smell nutty.
Stir in the green chilies, dried red chili, curry leaves, and asafoetida. Let them sizzle for 30 seconds until highly fragrant.
Turn the heat to low. Add the grated coconut and sauté for 2 minutes. Do not let the coconut brown.
Add the cold cooked rice and salt. Gently fold using a lifting motion with your spatula to combine without breaking the grains.
Cover the pan and let it steam on ultra-low heat for 2-3 minutes until heated through. Serve hot.