Mix the above powders , dilute with 2 tablespoon water and keep aside.
Place duck fillets , skin side down on cutting board ; trim and discard excess fat. Place fillets , skin side down in large pan ; ( cook without oil ) cook over medium about 10 minutes or until skin is browned and remaining fat melted. Turn fillets , brown other side; drain on absorbent paper.
Heat oil in a pan or heavy bottomed vessel. Add finely sliced onions and crushed garlic. Stir fry until onions are browned lightly. Add green chillies, ginger and curry leaves. Saute slowly for 3- 4 minutes.
Add chilli powder- turmeric powder- coriander mix. Stir over low heat until fragrant. Add garam masala powder , saute again for 2 - 3 minutes until fragrant.
Return duck fillets to pan , stir to coat in spice mixture. Stir in vinegar, thin coconut milk and salt. Cover with a lid and cook on a medium heat for 45 minutes to 1 hour or until fillets are tender .
Finally add thick coconut milk. Mix it well. Do not boil again. Serve with Appam. You can follow the same recipe for Chicken Mappas.