1. Soak tamarind in 1/2 cup of warm water and set aside.
2. Heat oil in a pan, temper mustard seeds.
3. Add sliced onions, ginger and garlic.
4. Sprinkle some salt.
5. Fry till onion turns golden brown.
6. Extract water from tamarind.
7. It should be thick.
8. Add it to the onions.
9. Add turmeric powder, red chilli powder, more salt and allow the mixture to cook for about 10-15 minutes or until the raw smell of tamarind goes off and oil starts to float on top.
10. Finally add jaggery powder and mix well.
11. Serve hot with chapathis/pooris.

Courtesy: http://spicesetc.blogspot.com/