First of all, boil potatoes and cut them in dices. Small square pieces.
Put 3 tsp oil. Add mustard seeds when they crackle add cumin seeds and then curry leaves. Saute them for a while.
Grind green chillies and garlic cloves together and add the paste in oil. Saute for 1 min. Now add potatoes in it and mix well.
Add turmeric powder and Coriander powder, salt and some water to adjust consistency and all the masalas coat well the potatoes.
Mash some pieces of potatoes and mix well. Add sugar and switch off the flame then add lemon juice and Coriander leaves.
Enjoy the lovely potato simple shak with puri.
