In a heavy bottom pot,warm up the oil. Temper the oil with mustad seeds. Once they crackle, add the hing, chana & urad dal. Cook till the lentils are browned in color.
Add the dried chillies and methi seeds next. Saute fo r5-6 seconds till they swell a bit.
Add curry leaves to the oil, they will immediatley splutter so be careful. Saute for 2-3 seconds and add all the vegetables that you are using at once. Sprinkle a pinch of salt. Saute the vegeatble for a minute or so with the spices.
Next sprinkle the sambar powder and red chilli powder (if using) and saute for 20 seconds.
Add the cooked mashed lentils next and mix well. If you feel that they are thickish, add water to thin out as per desired consistency.
Mix well and let come to a slow boil on medium heat. Reduce the heat and add the tamarind and jaggery. Taste and adjust the salt. Mix well.
Let simmer for 10-12 minutes on low medium heat stirring a bit in between. Initially you will see that there is a layer of foam on the sambar but as it cooks out, the color will deepen so will the flavors. Rest for 30 mins and serve warm!