Step 1

Arrange 2 racks to divide the oven into thirds and heat the oven to 450°F.

Step 2

Fill a large bowl with cold water. Cut 4 russet potatoes lengthwise into 1/2-inch-thick planks. Stack the planks and cut lengthwise again 1/2-inch-thick fries. Place the fries in the cold water and let soak for 5 to 10 minutes. Drain. Place on paper towels and pat with more paper towels until very dry.

Step 3

Transfer the potatoes to 2 rimmed baking sheets. Drizzle 2 tablespoons olive oil and sprinkle 1/8 teaspoon kosher salt onto each baking sheet of fries. Toss to coat and spread out into an even layer.

Step 4

Roast the fries for 10 minutes. Rotate the baking sheets between racks and from front to back. Roast until the bottoms of the fries are golden-brown, about 10 minutes more. (If the bottoms are not browned, roast a few minutes more.)

Step 5

Using a thin metal spatula, flip the fries. Rotate the baking sheets between racks again. Continue to roast until browned and tender, 7 to 10 minutes more. Meanwhile, finely chop 1 small bunch fresh chives until you have 3 tablespoons.

Step 6

Transfer the fries into a large bowl. Sprinkle with the chives and 3 tablespoons finely grated Parmesan cheese, and drizzle with 1 teaspoon truffle oil. Toss to combine. Taste and season with more kosher salt and more truffle oil to taste as needed. Serve immediately with ketchup for dipping.