Soak the tamarind in 1 cup of hot water for a 10-15 minutes then squeeze the tamarind to extract the juice and filter the tamarind juice to get the extract.
Peel the ginger and chop finely, pour the chopped ginger into salt water and keep it there for 5 minutes,and drain it.
Heat coconut oil in a kadai and fry the ginger until its brown. Remove the fried ginger on to tissue paper to remove the oil and keep it aside.
Grind the fried ginger in a mixer grinder to get it finely crushed. Take a kadai and pour the tamarind juice,add salt,chilly powder and turmeric powder and combine well.
Bring to boil, Reduce the flame to low and cook for 10 minutes,so that the gravy gets thick. Add 1 cup of hot water with jaggery and mix well,filter it and keep that aside.
Heat oil in a pan,add mustard seeds, when it splutter add chopped onion,chopped dry red chilly,chopped green chilly and curry leaves and saute till brown colour.
Pour this mixture to the cooked tamarind water. Add the crushed ginger and jaggery water , reduce the flame allow the mixture to boil to a thick consistency.