From Modernist Cuisine: "The Perfect Fry"
Cut potatoes into batons and rinse them to get rid of surface starch. Vacuum-seals them in a plastic bag, in one even layer, with water. Heat the bag to 212 degrees for 15 minutes, steaming the batons. Then hit the bag with ultrasound to cavitate the water—45 minutes on each side. Reheat the bag in an oven to 212 degrees for five minutes, and put the hot fries on a rack in a vacuum chamber, and then blanche them in 338-degree oil for three minutes. When they’re cool, deep fry the potatoes in oil at 375 degrees until they’re crisp, about three more minutes, and then drain them on paper towels. Total preparation time: two hours.
Or you could just blanch in 325 oil and finish in 375. Your choice