Boil and peel potato,mash roughly.
Heat a pan,add ghee.Add hing and chopped onion.Add green chilli.
When potato is brown,add ginger -garlic paste mix well,Add all spices and salt exept garam masala powder and amchur powder.Add 1cups water,cook for 4-5minutes on medium flame.
Oil leaves the edges of pan,add curd,mix and cook for 2-3 minutes on low flame.
Add potatoes,mix.Add 2cups water,cover and cook on low flame for 12-15 minutes.
Now gravy is thick.Add garam madala and amchur powder,mix.Add 1more cup water.Cook on low flame for 2-3 minutes.
Serve with puri/parathe.
