Heat oil in a non-stick pan till smoking point. Allow it to cool for a while.
Cut dried red chillies into pieces, remove extra seeds and place in a grinder jar along with crushed coriander seeds.Grind coarsely.
Add mustard seeds to the pan. Cover and let them crackle.
Remove lid, add onions and sauté till soft.Add green chillies and ground powder. Mix well and cook for 1 minute.
Add garlic and mix well. Add coriander powder and cumin powder. Mix well.Add potatoes, salt and amchur.
Mix well and cook for 1 minute more.Sprinkle a little water, mix again and cook for 2 minutes. Serve hot.