Place the potatoes in a large pot with enough cold water to cover them, then bring the pan to a boil. Add the salt, then boil the potatoes until just cooked but still firm inside when tested with a skewer. This will take around ten minutes. Drain, then set the potatoes aside to dry and cool.
Whilst the potatoes are boiling, heat a small pan over medium heat. Add the coriander and cumin seeds and toss gently until the seeds start to colour and become aromatic. Remove from the heat, allow to cool then grind to a fine powder.
Place cooked potatoes, salt, ground cumin and coriander, turmeric, amchur, asafoetida and chilli powder in a bowl. Shake and toss well to cover potatoes evenly. This will also fluff the edges of the potato to help crisping.
to cook
In a wide pan, heat the oil and add the mustard, cumin and fenugreek seeds and fry until sizzling.
Add the potato and stir gently to coat in the oil. Cover and cook the potatoes on medium-low heat for around ten minutes, or until golden and crisp. Toss occasionally to evenly brown the potatoes.
Whilst the potatoes are frying, put the peas in a small bowl of boiling water. When the potatoes are cooked, drain the peas, add to the potato, and gently combine. Fry for another minute.
to serve
Stir in the sesame seeds and chopped coriander. Toss to coat potatoes and peas completely. Serve
notes
Amchur, or dried mango powder, is readily available from Indian grocers.
Setting the par-boiled potatoes aside to dry helps the crisping process.