In a karahi (deep round pan), heat oil, add cumin seeds and asafoetida. When it starts to splatter add coriander powder, turmeric powder, salt and red chilli powder. Quickly stir and add tomatoes. Fry for a minute. Do this on a low medium flame else the masala will get burnt. Add chopped cauliflower, potatoes, green peas and ginger. Mix in all together. Add 1 cup water and switch the flame to high and cover with a lid. After 5 minutes turn the flame to medium and let the vegetables simmer cook until they are soft. This should take approximately 20 minutes. Check once or twice occasionally in between. When the vegetables are tender take the lid off, turn the flame higher and add dry mango powder. Mix in gently. There should be no water left and should be able to see some oil on the sides. Garnish with coriander leaves and green chillies.