Wash the tamarind clean. Place the tamarind, jaggery, sugar, dates and water in a deep boiling pan. Soak for a few minutes. Put to boil for about 7-8 minutes. Cool to room temperature. Blend in a mixie till smooth. Strain and transfer to the pan again. Boil till thick enough to coat the back of a spoon thinly. Add the seasoning. Cool again. Store in clean airtight bottles and refrigerate.