For the Batter Base

1. Add both the rice to a mixing bowl. Wash well until water runs transparently. Cover rice with water, close with a lid and let it soak for around 6 hours or overnight
2. Wash the urad dal well and soak it in water for 3 hours
3. Discard water from both the dal and the rice
4. Add washed urad dal to a grinder or a food processor (mixer). Grind until it is a coarse paste
5. Add the rice on top of the urad dal paste, a little water and grind again to a slightly coarse batter
6. Pour batter in a clean mixing bowl
7. Add the salt and mix well
8. Let the batter ferment for around 8 hours (or until it doubles in volume)

For tempering the Batter

1. Heat Ghee in a small pan
2. Add the mustard seeds, let them splutter
3. Add the black peppercorn, dry ginger powder, cumin seeds, cashews, asafetida powder, green chili. Fry for 1-2 minutes until cashews turn golden
4. Add curry leaves and fry for 10 seconds
5. Pour the tempering onto the batter. Add the coconut (optional)
6. Mix well, adjust seasoning if required

Steaming the Kanchipuram Idli

1. Grease a round pan or idli plate or heat-proof bowl/glass/tumbler with ghee or vegetable oil
2. Fill the pans half full with the idli batter
3. Bring some water to a boil in a steamer or cooker
4. Place the pan with the batter carefully onto the steamer or cooker
5. Close with the lid
6. Cook for around 20 minutes on medium heat or until the idli is well cooked
7. To check, insert a knife or toothpick into the center of the idlis. If it comes out clean without leaving any wet batter, it is done!
8. Let the idlis rest at room temperature for around 10 minutes
9. Using a knife, loosen up the edges of the pan
10. Carefully remove the idli from the pan 
11. Serve as is or with your favorite condiment
12. If you have leftovers, store them in the refrigerator for up to 3 days. Reheat or steam before eating