Boil potatoes with some salt added to it. Then peel them off and mash the potatoes to a paste. Heat the oil in a pan and add mustard seeds,cumin seeds,red chillies and when they start to pop up,add green chillies and finely chopped ginger pieces. Then add the mashed potatoes to it and cook until it gets brown. When it cools a bit, add 2 tsp. of lemon juice to it. Note: Add saffron to the oil first, so that the potatoes dont stick to the pan.