Instructions: Peel potatoes. Using a paring knife, trim each into a uniform oblong with flat sides and a flat bottom. Starting with the flat bottom, slice the potatoes on the straight blade of a mandoline into uniform thin slices 1/4-inch thick (or slice by hand into identical slices just a bit thicker than 1/8 inch). Place slices in a bowl of cold water as you slice them to prevent the flesh from discoloring.

Pour oil into two deep skillets to a depth of at least 1 1/2 inches. Place pans next to each other on stovetop. Heat oil in one to a steady temperature of 300 to 320 degrees and the other to 360 degrees. Measure temperatures frequently with a deep-frying thermometer. Line a baking sheet with parchment paper; set aside.

Dry potato slices well on paper towels. Layer them in paper towels, and keep them covered while frying in batches. Slide about 15 slices into the 300 degree oil. Begin shaking pan very lightly to move slices around. Be careful not to splatter hot oil; only a small movement is necessary.

Adjust heat to maintain temperature at 300 to 320 degrees. Cook slices, shaking skillet gently but continuously, until small blisters begin to form on surface of slices, 3 to 4 minutes. If slices are browning, remove pan from heat briefly to cool oil slightly (continue shaking), then return to heat.

With a skimmer, scoop up 4 or 5 slices from first pan, and allow oil to drip off for 6 to 8 seconds so potato slices soften slightly. Lower skimmer into hotter oil in second skillet, allowing slices to puff in oil for a second or two, then lift them out immediately. Place slices that have fully puffed on lined baking sheet to rest until final frying. (Slices that didnt inflate should be set aside to eat; they can be fried again just to brown, if desired.)

Remove remaining slices from first skillet, 4 or 5 at a time, and fry as above in hot oil. Place all inflated slices on baking sheet, and cover with a towel or plastic wrap. Repeat entire process with remaining raw slices of potatoes, frying 15 at a time. Can be made ahead up to this point and held at room temperature for several hours.

When ready to serve, reheat oil in one skillet to 350 to 375 degrees. Line a baking sheet with paper towels. Place reserved cooked slices, 8 or 10 at a time, in oil. They will inflate again and begin to brown. Keep turning over and stirring with skimmer until they are evenly colored and crisp on the outside, about 1 minute. Remove to baking sheet. Keep in a warm spot while frying remaining slices. Season with salt, and serve in a napkin-lined bowl.

This recipe yields 4 servings.

Comments: In 1847, a chef from the French village of Saint-Germain-en-Laye prepared french fries for a local banquet to be held in honor of King Louis-Phillippe. When the royal train was delayed, the chef tried to reheat the cold potatoes by cooking them in a hotter pan, which caused them to balloon with steam.

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