Heat half of the mustard oil and fry the boiled potato pieces till golden in color.
Pour the remaining oil in the same kadai and heat it through. Add crushed coriander seeds and cumin seeds.
Add ginger paste and fry it lightly. Now add the tomato paste and fry really well till the raw smell evaporates.Add salt, chilli powder, sliced green chillies mixed with little water and fry till oil comes out of the masala.
Add the fried potatoes to the masala and toss them well so that all the potatoes are well coated.
Add some hot water and let it boil for some time. Adjust the seasoning and let the gravy thickens. Add handful of chopped coriander leaves. Server after sprinkling some roasted masala powder over it.