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1
Peel the potatoes and slice on a mandoline to a uniform 3 mm thickness, cutting in long oval sections. Discard any slices that are irregular, torn, or marked by blemish. Submerge the slices in cold water and soak for 15 minutes, then drain. Lay between two clean kitchen towels and dry meticulously: no surface moisture must remain. The slices are ready when the towel shows no further dampness on contact.
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2
Set the first vessel of oil to 150°C and verify with a thermometer. Lower 6–8 slices into the oil in a single, uncrowded batch. Fry for 6–7 minutes, agitating the basket gently throughout. The slices should colour only very faintly and develop irregular surface blisters — the early signs of the gelatinised crust forming. Lift out, drain briefly, and allow to cool for 2–3 minutes before proceeding. At this stage the cooled slices may be held at room temperature for several hours or refrigerated overnight for service to order.
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3
This is where the dish lives or dies. Set the second vessel of oil to 190°C and verify. Plunge the cooled first-fried slices immediately into the hot oil. Within 10–20 seconds the interior moisture converts explosively to steam: the gelatinised crust expands and each slice inflates into a hollow, golden pillow. Remove each slice the instant it is fully puffed and uniformly golden — do not hold them in the oil beyond that point. Accept that 30–40% of slices will not puff; set those aside.
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4
Season the puffed slices immediately with fine salt and transfer to a folded white napkin in a warm silver timbale. Serve within 2 minutes: the hollow steam chambers begin to collapse and the slices return to ordinary fried potato beyond that window.