Pressure cook thoor dhal with garlic and mash well. Steam the chopped vegetable with onions, tomatoes, turmeric powder and salt. Mix the cooked thoor dhal and steamed vegetables together. Add tamarind extract, red chili powder, asafetida and sambar powder. Boil this until the raw smell of tamarind vanishes.
Heat oil in a small pan. Add mustard seed. When it starts to pop add urad dhal and fry until it becomes golden. Remove from fire. Pour this seasoning over the sambar mixture. Heat for 5 more minutes. Garnish with chopped coriander leaves.