Slice potatoes as thin as possible.
Cut potatoes into thin slices, using a mandoline or sharp knife; rinse with cold water.
Bring vinegar and 6 cups water to a boil in a large saucepan over high heat. Add sliced potatoes, and cook 3 minutes. Drain potatoes, and spread on a paper towel-lined baking sheet. Pat dry with paper towels, and chill 15 minutes.
Meanwhile, pour oil to a depth of 3 inches into a large Dutch oven, and heat to 340°. Fry potatoes, in batches, stirring occasionally, 3 to 4 minutes or until golden brown. Drain on paper towels, and immediately sprinkle with chives and desired amount of kosher salt.