Wash and clean rice. Add 1 cup Kerala brown rice and 4 cups water in the pressure cooker and soak for half an hour.
Pressure cook for 30 minutes (reduce the heat from high after 3 quick whistles and cook on a medium heat for 25 minutes). Do not open the pressure cooker lid immediately. Allow the cooker to cool naturally.
Wash and soak cherupayar in 2 cups water (400 ml) water for 6 hours (or overnight).
Transfer soaked cherupayar (along with its soaked water) into a pressure cooker (final water level after soaking should be 1/2 inch above cherupayar). Close the pressure cooker lid and cook on high heat for 3 whistles. Switch off the heat. Allow the cooker to cool naturally. Open the lid. Boiled cherupayar will be thick in consistency.
Heat oil in a pan. Add mustard seeds. When they crackle, add jeera and urad dal. Saute on a low heat for 1 minute.
Add boiled cherupayar and grated coconut mixture and adjust salt to taste. Do not add water when cooking. Cover with a tight lid and cook on a low heat for 10-12 minutes. Serve as a side dish with kanji.