Soak the cut potatoes in hot water, 1 tsp salt and turmeric for 30 minutes
In a heavy bottomed pan placed on medium heat, add the ghee or oil and once hot add the mustard seeds. Once they splutter, add the curry leaves, green chilly and asoeftida.
Stir on medium low, then add the chilly powder and salt. Mix well.
Drain the sweet potatoes and add it to the pan. Set the heat and stir well so that the vegetable is well coated with the spices. Stir for 3-5 minutes.
Reduce the flame, add 1/4 cup water, cover and let the potatoes cook for 10-12 minutes till soften.
Check for salt, uncover and then cook on low to medium low heat for 20 -30 minutes stirring occasionally till the potato crisps up.
Turn off the heat. Sprinkle the lemon/ lime juice, mix well and serve.