Marinate chicken with curd and salt for 2 hours.
Heat oil in kadai, add mustard seeds. When it splutters, add onion and curry leaves.
When onions are lightly brown, add ginger, garlic, and saute for a minute.
Add chicken, half of the ground masala, and salt. If using grated or desiccated coconut, add in.
Mix them, cover with a lid, simmer and cook till the chicken is almost done, for about 15-20 minutes at least. Keep sauting occasionally to avoid charring.
If using coconut milk, add it now, and simmer for five more minutes till well combined and cooked.
Lastly, add the reserved half of the ground masala and give it a nice stir.
Keep it covered for 5-10 minutes before serving, to help the flavors combine well. Serve it with plain steamed rice or Malabar Paratha.