Parboil the potatoes in a large pan with a pinch of salt and the TRS turmeric powder, this usually takes about 5 minutes.
Drain in a colander and place a kitchen towel over the top of the colander, so that the potatoes steam dry. Set aside.
Place a large sauté pan on a low heat and add the oil. Once the oil is warm, add the TRS mustard seeds, TRS fennel seeds, TRS nigella seeds, asafoetida and TRS ajwain seeds. Stir well into the oil, then stir in all of the remaining key spices, and fry until fragrant.
Add the TRS tomato paste, TRS garlic and ginger. Stir and fry for 1 minute.
Add the potatoes, coat and stir really well. Ensure that the potatoes are cooked through, and a little crispy on the outside.
Add the TRS fenugreek leaves, TRS mango powder, TRS mint leaves, and tamarind pulp.
Cook for a further minute, remove from the heat, place a lid on the pan and leave for 10 minutes.
Add fresh coriander, and serve with chapattis and a little natural yogurt