To check that the oil is hot enough, sprinkle in a few mustard seeds, if they pop the oil is ready. Then add the remainder of the mustard seeds.
Add the chilli and turmeric powders to the sizzling seeds, and salt to taste.
Fry this pungent mixture of oil and spices for 1 minute then add the potatoes. Fry for about 4 minutes until the potatoes are smothered in seeds and appear to have crispy edges. They will look quite yellow in colour. Cover the pan and on a low heat, cook the potatoes for a further 5 minutes.