Peel the potatoes, if desired; cut into 1/2-inch-thick matchsticks. Place in a bowl of cold water to soak for 10 minutes.
Heat the oil in a large saucepan (at least 5 quarts) to 325°F. Remove the potatoes from water; dry very well with paper towels. Working in batches, blanch potatoes 2 minutes (they will not take on any color). Drain well; cool completely on pans lined with paper towels.
Raise the heat of the oil to 375°F. Preheat the oven to 250°F. Working in batches, fry potatoes until golden, about 3 minutes. Drain well; place on a rimmed baking sheet. Sprinkle with salt; keep warm in the oven while frying the remaining potatoes. Serve immediately.
