Heat oil in a cooking vessel, add mustard seeds and as they sizzle, add ginger garlic paste and fry for 2 mts.
Add coriander pwd, turmeric pwd and salt. Combine. Add the chicken pieces and fry till they are slightly browned approx 8-9 mts. Remove the chicken pieces and keep aside.
In the same vessel, drizzle some more oil, if required, add the browned onion paste and ground masala paste and saute for 2 mts. Add the vinegar and jaggery mixture and combine.
Add 1 1/2 cups of water and the browned chicken pieces and cook till the chicken turns soft and it forms a thick gravy.
Serve hot with rice or rotis.