Cook the tur dal till done and mash well. Heat one tbsp oil in a heavy bottomed pan. Add the methi seeds and fry till light red. Add 1/2 tsp urad dal and fry till the urad dal too is light red. Add the red chillies and coriander seeds and fry till well roasted. Add curry leaves and grated coconut and fry for a few minutes. When cool, grind in a mixer to a fine paste, adding a little water. Clean and peel the onions (keeping them whole). Heat one tbsp oil in a heavy bottomed pan. Add 1/2 tsp mustard seeds. When they splutter, add 1/2 tsp urad dal and asafoetida. Fry for a minute. Add sambhar onions, green chillies and curry leaves. Also add vegetables of your choice. Fry well till you get a nice aroma. Add a little water, cover and cook till the vegetables are done. Soak the tamarind in a little water and extract the pulp. Add it to the cooked vegetables. Bring it to a boil. Add salt and jaggery and cook till the raw smell of tamarind disappears. Add the mashed tur dal and the ground masala paste. Mix well, add a little water if required. Simmer for a couple of minutes. Serve hot with rice or dosa. Can add vegetables like lady fingers, brinjals, pumpkin and drumsticks to the sambhar.