Heat oil in the pan until hot. Add in the mustard seeds and let it splutter. Add in the curry leaves and onion and fry till the onions are soft.
Add in the slit dried red chillies, and the chicken pieces. Add in the salt and red chilli powder. Add 1 cup of water. Mix well to combine. Cover the pan with a lid and let it cook in low flame for 15-20 minutes. Stir once a while so the chicken does not scorch at the bottom.
After 20 minutes, remove the lid and fry for 5-10 minutes until the chicken is almost dry.
Add in the fresh shredded coconut and saute for a couple of minutes.
Add in the curry leaves and remove from heat. Chicken Chinthamani is ready.