In a heavy bottom saucepan, heat oil; add the mustard seeds, methi seeds and hing. Once the seeds start to splutter, add the curry leaves and chopped leeks. Cook for about 3~4 minutes.
Add the grated coconut, mix well and cook for a minute.
Now add the tamarind paste, salt and let it simmer for about 3~4 minutes.
In the mean time, whisk sambar powder in ½cup water and add to the pan. Simmer for 2~3 minutes.
Stir in the cooked toor dal along with 1~2 cups of water depending on the desired consistency. Bring to a boil and adjust the seasoning. Add a tiny bit of jaggery if desired. Garnish with chopped cilantro and serve with steamed rice.