Soak yam in water for about 15 minutes for the mud to melt off. Wash thoroughly.
Peel and chop to 1 inch pieces and add them to a pot of water.
Boil yam until fork tender yet firm and not mushy. Do not over boil. Drain them. Or you can also cook the whole yam in pressure cooker with little water for 3 to 4 whistles. Once cool peel off the skin and chop to pieces.
Heat a pan with ghee. Add curry leaves, green chili and fry till crisp.
Add cumin and mustard, when they splutter add hing. Stir in the ginger garlic and saute for 30 seconds.
Add cooked yam pieces, salt and turmeric.
Fry on high heat for 4 to 5 mins. , Keep stirring to prevent burning. If needed add little more ghee.
Add pepper powder or red chili powder, garam masala and fry for a min or 2.
Serve yam fry with rice. You can squeeze in some lemon juice.