Wash and slice sweet potato in thick roundals or pieces.
Add 1 glass of water and pressure cook for 3 whistles or cook till it become soft.
Peel the skin and roughly mash the sweet potato or chop into pieces.
In a pan add curd and 1 cup water and whisk well.
Add all the dry spices , mashed sweet potato, green chili and ginger in it.
Mix well and cook on medium flame for about 7-8 minutes.
Keep stirring in between to avoid curdling.
Heat oil in a small pan and add cumin and mustard seeds.
When cumin start crackling add asafoetida and switch off the flame.
Add red chili in the tempering and pour over the boiling curry.
Remove the curry from the heat and add chopped coriander and lemon juice.
Mix and serve hot.
Serving suggestions- goes well with any Indian bread specially poori or paratha.