Heat the oil in a deep pan or wok. Fry the mustard seeds, cumin seeds, onions and ginger while stirring for 1-2 minutes. Add salt and turmeric and continue frying for 5 minutes. Then add the cauliflower and stir well. Add the tomatoes and the chilli pepper, season with sugar and the ground cumin and continue to cook over a low flame, stirring constantly, until the cauliflower is firm to the bite.
Season with salt and serve sprinkled with fresh chopped parsley.