Step 1Using a mandoline or vegetable slicer, cut unpeeled potato into long matchsticks. Immediately place in bowl filled with generously salted water.
Step 2Heat about 1 1/2 inches oil in large shallow saucepan. When the oil reaches 375 degrees, you're ready to add potatoes. Drain the strips and blot dry. (If you don't have a deep-fry thermometer, you can toss in a sacrificial fry. If it starts bubbling right away, the oil is hot enough.)
Step 3Fry strips just until they soften and start to look a bit translucent, about 3 minutes. Remove fries with a slotted spoon and drain on paper towels. Sprinkle with a little salt, then let stand about 5 minutes. Place fries back in hot oil carefully (oil will bubble up quite a bit.) Finish cooking until fries are pale golden and crisp, about 4 minutes. Again, drain on paper towels and sprinkle with a little more salt.