Cut the potatoes into small cubes, cook and keep it aside.
In a pan, add coconut oil, add mustard seeds, garlic, ginger and green chillies and fry for 2 minutes.
Add onions, fry till translucent, add chopped tomato, fry for 3 minutes. then, add cooked potatoes, add coriander leaves and mix well.
Transfer the same into a wok.
In the same pan, add prawns, turmeric powder and little salt and fry the same.
(If the prawns leave water, transfer the water to the wok where you have transferred fried ingredients)
Add coriander powder, jeera powder, chilli powder to the pan and fry the prawns for about 3 minutes.
Add these fried prawns to the ingredients in the wok, add lemon juice or vinegar.
Mix well on a slow fire for about one minute.
Serve hot as a dish with rice and dal-bimbli sar/sambar or chapatis or rotis.