In hot water soak the red chillies for some time. After that remove from water and blend with all dry spices mentioned in list along with vinegar, water as required.
Heat oil in a pan. Shallow fry the sliced mushrooms and potatoes separately.
Remove once they are light brown and well fried and keep on paper tower to soak excess oil
Add 2 tbsp oil to the pan. Add chopped onion, green chilli and saute till translucent.
Add the spice paste and saute well. add salt and cook till the paste is cooked and leaves oil.
Add shallow fried mushrooms & potatoes to the paste. Add ¼ cup water and stir well. Let it simmer for some time.
Add chopped coriander leaves and turn off heat. Serve with flatbread.