Put 2 tablespoons of the peanut oil in a pan, add the mustard and cumin seeds, cinnamon, chilli and cardamom. Stir-fry until aromatic, then stir in the turmeric. Add the potatoes, salt and pepper and stir-fry for about 2 minutes. Add 250 ml water and boil until the liquid has evaporated and the potatoes are tender - add more water if necessary. Sprinkle half the chopped onions over the top and add most of the coriander, reserving a small amount to garnish.
Put the remaining oil in a frying pan, add the onion and the garlic and fry until golden brown. Pour the contents of the pan, and the oil, over the potatoes and toss to coat. Top with the torn coriander and serve. Squeeze lime juice over the salad to your own taste.
