Cut the duck into medium sized pieces, wash well and soak them in a little salt and turmeric powder for couple of minutes and squeeze out the excess water and drain it.
Marinate the cleaned duck pieces with the ingredients given in To Marinate for at least 30 minutes. Heat a pan or in pressure cooker, pour coconut oil.
Add mustard seeds and when it starts to splutter, add sliced shallots, curry leaves, dried red chilly,chopped ginger,garlic and saute for couple of minutes.
Add chopped onion, green chillies, satue till onions turn translucent and light brown color.
Add the marinated duck pieces, salt to taste, cover pan and cook over low heat for 30-45 minutes till duck is half done or if your using pressure cooker, close the cooker and pressure cook until you hear about 5-6 whistles on high heat.
Mix turmeric powder, red chilly powder, coriander powder and garam masala into the thin coconut milk and mix well.
Pour in spiced coconut milk into half cooked duck and adjust the salt. Lower heat and simmer gently till duck is cooked and gravy has thickened.
Open and add the thick coconut milk and stir gently. Cover and cook for another 2 mins and remove from the heat.