Soak tamarind in water for about 1/2 an hour & drain to get the juice.
Mix tamarind water, jaggery, chopped ginger & green chillies and allow it to boil, until required consistency is obtained.
:- The gravy must be thick.
Heat oil in a pan.
Splutter mustard seeds.
Add dry red chillies and curry leaves to this & mix it with the gravy.
In a dry pan, fry the fenugreek seeds and grind to a fine powder.
Add this powder into the gravy and stir well.
Allow it to cool & keep it in an airtight container.
:- This can be keep in fridge for one or two months.
:- Serve with rice.