Wash and soak tamarind in warm water for 10 mins. Squeeze the tamarind well, and extract pulp (approx 1500 ml).
In a pan, roast Channa dal, chillies, black pepper, red chillies and curry leaves in 2 tsp of oil one by one. Let the curry leaves shrivel a bit. Cool, powder it slightly smooth. Keep aside.
In a deep bottomed pan (or kadai), add 3 TBSP of oil.
Splutter mustard seeds, toor dal, asafoetida, turmeric , and methi seeds. Let the methi seeds not burn else will give a bitter taste.
Now add the tamarind pulp, salt, jaggery, 2 cups of water and bring it to rolling boil.
Now add the powdered spice mix and saute for 2 mins on low flame)
If its thick on its own, then no need to worry. If its too watery and you need to thicken it, make a slurry of rice flour in 2 tsp of water and add to the boiling mixture. It will thicken in 3-4 mins.
Now transfer to serving bowl, add 3 tsp more of sesame oil. cover and use after 2 hours (it tastes better after 3-4 hours).
Serve with Arisi Upma (broken rice savoury Upma / Pudding) or steamed rice and any dry curry.