French Fries or Frites

add the potatoes to a large bowl filled with enough cold water to cover them completely. Let sit covered in the refrigerator for at least 30 minutes, up to 16 hours.
Drain the potatoes and lay them out on clean, dry, lint-free kitchen towels and pat dry.
Transfer the potatoes to a large mixing bowl, sprinkle the cornstarch, and toss to coat well. The cornstarch coating is essential for a crisp exterior, so do this properly. Transfer to a baking sheet lined with a wire rack and let sit for 30 minutes. You might need to use two baking sheets to prevent the frites from sticking. The cornstarch will dry and form a thin white coat on the potatoes. 
While the potatoes dry, heat the oil in a Dutch oven to 300F [150 C] over medium heat. Cook the frites in batches. Add the potatoes and leave them in the oil for 4 minutes. Remove them with a slotted spoon or spider and transfer them to the baking sheet lined with the wire rack. They will be cooked from the inside but not golden brown and crisp. When ready to serve the steak and frites, heat the oil in the Dutch oven to 350F [180C], and fry the potatoes until light golden brown and crisp, about 4 to 5 minutes. Transfer to a large mixing bowl and sprinkle salt on the hot fries. Toss to coat well and serve immediately.