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1
Prick each baby potato all over with a fork so the heat travels into the centre during frying rather than being trapped beneath the skin, which would cause it to blister and burst. Place the pricked potatoes in salted cold water for 10 minutes, then drain and pat them completely dry, because any moisture left on the surface will cause the hot oil to spit violently the moment the potatoes go in.
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2
Heat the oil in a deep, heavy pan to approximately 170 °C — a small piece of bread dropped in should brown steadily in 30 seconds. Deep-fry the potatoes in batches so the oil temperature does not drop and the skin sets to a firm golden shell that will hold its shape through the long braise to follow, then remove and drain on a rack.
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3
In a heavy-based pot large enough to hold all the potatoes in a single layer, warm 3 tablespoons of the frying oil over medium heat. Add the asafoetida and let it bloom for just a few seconds until the sharp, raw sulphurous note softens into something rounder and allium-like, then add the ground fennel and dry ginger and stir for 30 seconds until the kitchen smells of warm spice rather than raw powder.
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4
Reduce the heat to its lowest setting, add the Kashmiri chilli powder, and stir for 20 seconds so the oil turns a vivid scarlet-orange and the colour is drawn fully into the fat. Do not allow the chilli to darken at the edges — darkening signals burning, and the sauce will taste bitter and look dull rather than carrying that characteristic deep, clean red.
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5
This is where the dish lives or dies: remove the pot from direct heat momentarily and add the whisked yoghurt in a thin, steady stream, stirring constantly so it folds smoothly into the spiced oil rather than seizing into pale, grainy curds against sudden high heat. Return to the lowest flame and stir continuously for 3 to 4 minutes until the sauce tightens, turns a deep glossy red, and the oil begins to separate at the edges — the moment when the raw yoghurt smell disappears entirely and you know the sauce is cooked through.
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6
Add the fried potatoes to the sauce and turn each one thoroughly so every surface is coated in the thick red paste, then season with salt. Seal the pot tightly — press a sheet of foil under the lid if the fit is loose, so the steam trapped inside does the work of driving the sauce deep into each potato — and set the pot over a tawa or heat-diffusing plate on the absolute lowest heat available for a minimum of 20 minutes, until a gentle shake of the pot shows no pooling liquid, only a thick coating on each potato.
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7
Remove from the heat and rest, still sealed, for 5 minutes so the sauce that has loosened at the base redistributes evenly around each potato as the pot cools slightly. Uncover and check that every potato wears a vivid scarlet paste with little or no pooling at the bottom — any orange or pale-pink tone tells you the yoghurt sauce needed more time to reduce before the dum began.