Parboil the potatoes and set aside.
Heat the clarified butter in a heavy-based pan and add the cumin seeds.
When they splutter, add the ginger. When the ginger begins to brown, add the yoghurt, a tbsp at a time, stirring vigorously till the fat separates between each addition.
Add the cauliflower, potatoes and green chillies
Stir-fry the vegetables over high for 2-3 minutes till they get coated with the clarified butter.
Then add the chilli powder, turmeric, garam masala, coriander powder and salt. Stir a few more times, till well mixed.
Lower the heat, cover the pan and let the vegetables cook till tender, stirring 2-3 times.
Serve hot, garnished with chopped coriander leaves.