Heat oil in a heavy based kadhai/pan and fry the onions till they turn pale (pink/translucent) - do not fry them too much, we just want them to lose their rawness. Add the chopped ginger, garlic, green chillies and fry for half a minute.

Add the tomatoes, bafat powder and sprinkle a little salt and continue to fry till the tomatoes turn slightly mushy. Add the potato cubes and sprinkle a little water, cover the pan and cook till the potatoes are almost tender (not fully cooked)

Now add the cleaned prawns, salt to taste (remember you have added some salt to the tomatoes) and half of the chopped coriander. Cover and cook for 2-3 minutes or till the prawns are just done - overcooking will turn them chewy. When they are perfectly cooked prawns will not look raw (soft/supple texture) and the flesh will be more opaque than transparent (when they are raw) - when you bite into them they should be tender and juicy.

Remove from heat, garnish with the remaining chopped coriander and serve hot with rice.