Cook the potatoes: Boil or steam the potato cubes until they are fork-tender but still hold their shape.
Drain them thoroughly and transfer to a large mixing bowl to cool.
Marinate: Once the potatoes are cool, add the yogurt, minced ginger, and cayenne pepper. Gently fold to coat the potatoes completely.
Set aside to marinate for at least 30 minutes or up to 3 hours in the refrigerator.
Temper the spices: Heat the ghee or oil in a large nonstick or cast-iron skillet over medium heat.
When the oil is hot, add the sesame seeds, black mustard seeds, and cumin seeds.
Fry the potatoes: As soon as the seeds begin to pop and become fragrant (about 30 seconds), carefully add the marinated potatoes and salt.
Fry, stirring occasionally, for 5-7 minutes, or until the potatoes are golden brown and have a light crust.
Finish and Serve: Turn off the heat and stir in the fresh lemon juice and chopped coriander or parsley.
Serve immediately.
After boiling, let the potatoes cool completely before mixing with the yogurt.
Warm potatoes can make the yogurt runny and cause them to break apart during frying.
