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mandoline, thinnest workable setting — about 1.5 mm / one-sixteenth inch, guard on

russets into rounds of one thickness. Uniformity is not neatness here, it is the whole schedule: a batch finishes together or it does not finish at all, and a pot holding slices of two thicknesses gives you scorched wafers and leathery half-cooked discs out of the same scoop. A mandoline is the tool because it holds a setting; a knife can do it only if the edge is keen enough to part the potato rather than wedge through it, and a blunt blade wanders thick and thin across a single bulb. Cut the slices into cold water as they fall so they do not oxidise on the board.