Too often french fries are saturated with oil, flimsy, and tasteless. The sign of a good fry is when you bite through a crispy exterior to find a light and fluffy interior. This double-fry method will ensure successful french fries to serve with a burger, steak tartare, or steamed mussels. That is, if you can resist snacking on them first.
Peel the potatoes and cut them lengthwise into 1/4-inch-thick slices. Cut each slice lengthwise into 1/4-inch-thick sticks. Place in a large bowl and cover with cold water. Refrigerate for at least 30 minutes or up to 2 days. Fit 2 baking sheets with wire racks and set them aside.
Place the oil in a Dutch oven or a large, heavy-bottomed pot. Heat over medium-high heat until it reaches 300°F on a deep-frying/candy thermometer.
Meanwhile, line a work surface with a clean, lint-free kitchen towel or paper towels. Using tongs or your hands, lift the potato sticks out of the water and shake off any excess liquid. (Do not drain the potatoes in a colander or strainer.) Place the potatoes in a single layer on the towel(s). Pat very dry with additional towels and place the potatoes on one of the wire racks in a single layer (you may have to arrange a few in a double layer).
Working with a handful at a time, carefully drop the potatoes into the hot oil with your hands, a slotted spoon, or a spider skimmer and fry until just limp but not browned, about 4 to 6 minutes. Using a slotted spoon or spider, transfer the potatoes to the second wire rack in a single layer. Repeat with the remaining potatoes, letting the oil return to 300°F between batches. Let the fries cool to room temperature, at least 10 minutes.
Heat the oil to 375°F. Working with a handful at a time, add the partially cooked fries to the oil and fry until golden brown and cooked through, about 2 minutes per batch. Using a slotted spoon or spider, transfer the fries to the now-empty first wire rack. While still hot, season each batch generously with salt. Repeat with the remaining fries, letting the oil return to 375°F between batches, and serve immediately.