Heat 2 teaspoons oil in a pan. Add coriander seeds, red chilies and coconut. Sauté till a fine spicy aroma starts coming and coriander gets roasted. Let cool and then transfer this mixture to a mixer and grind well.
Heat 1 teaspoon oil in a deep pan and sauté onion, brinjal, okra, potato and drumstick. Now add water, tomatoes and toor dal and mix well and let boil so that the vegetables are well cooked. Then add the ground coconut –coriander paste, tamarind paste, red chili powder, turmeric powder and asafetida and keep heating to boil.
Heat 1 teaspoon oil in a pan, add mustard seeds and let splutter. Now add curry leaves and pour this on to the cooked sambar.