To begin with, roast the vermicelli in a tablespoon of oil. Do not to brown it too much. Remove from fire and keep aside to let it cool.
In the meantime, heat 1-2 tbsp of oil in a wok.
Add mustard seeds and let them crackle. Next cumin seeds, asafoetida, and the curry leaves. Cook for a few seconds.
Add in the chopped chili, garlic, and ginger. Cook for a minute.
Mix in the vegetables and onions and cook until a bit soft.
Add in salt, turmeric powder, coriander powder, cumin powder, and amchoor powder.
Add in the roasted vermicelli and mix well.
Add in water making sure it covers the vermicelli.
Cover the wok, reduce the flame, and let it cook until the water dries up. Keep stirring occasionally so that it cooks evenly.
Add in the sambar masala and mix well.
Serve hot.