01 - Rinse the cut potatoes under cold water to remove excess starch. Drain and pat dry thoroughly with a clean kitchen towel.
02 - Heat the vegetable oil in a deep fryer or large, heavy-bottomed pot to 350°F.
03 - Working in batches, carefully add the fries to the hot oil. Fry for 4 to 5 minutes until pale golden and just tender. Remove with a slotted spoon and drain on paper towels.
04 - Increase the oil temperature to 375°F. Return the fries to the oil in batches and fry for another 2 to 3 minutes, or until deep golden and crispy.
05 - Drain fries well and immediately toss with sea salt. Serve hot with ketchup on the side.