Marinate mutton with the ingredients for marination and keep it for 15 - 30 minutes.
Heat oil in a pan and splutter mustard. Fry onion, green chillies, ginger, garlic and curry leaves. Stir in powdered masala ingredients and stir well till oil starts separating from it.
Cook marinated mutton in a cooker until 2-3 whistles or until done. Keep it aside.
After the mutton is well cooked, transfer whole mutton along with the gravy into the frying pan and mix it with the paste and add coconut milk and cook till the gravy thickens.
Decorate with coriander leaves and serve hot. Good with rice or chappathy, Appam, Parotta etc.