Peel the russet potatoes if desired (peel for a cleaner look or leave skin on for more texture). Cut each potato into 1/4- to 1/3-inch thick matchstick fries. Rinse the cut fries under cold running water to remove surface starch.

soak

Place the rinsed fries in a large bowl and cover with the 6 cups cold water. Add 1 tsp coarse kosher salt to the water and stir. Soak for at least 30 minutes, up to 2 hours, in the refrigerator to remove more starch and help crispness.

dry thoroughly

Drain the fries and spread them on clean kitchen towels or paper towels. Pat completely dry. Removing moisture is essential to avoid oil splatter and to achieve crisp fries.

first fry (blanch)

Heat 2 cups of the neutral oil in a heavy-bottomed pot or Dutch oven to 300°F (150°C). If you don't have a thermometer, heat oil until a small piece of bread sizzles gently but doesn't brown quickly. Fry the potatoes in batches so they don’t crowd the pot — about 3–4 minutes per batch — until the fries are pale and just beginning to soften but not browned. Use a slotted spoon to transfer fries to a wire rack set over a baking sheet; sprinkle lightly with 1 tsp coarse kosher salt while they rest. Let cool 10–15 minutes.

second fry (crisp)

Raise the oil temperature to 375°F (190°C). Fry the blanched fries in batches for 2–3 minutes or until golden brown and crisp. Transfer to a wire rack or paper towels to drain briefly.

Truffle-Parmesan Toss

melt butter

While the second fry is finishing, melt the unsalted butter in a small saucepan over low heat or in the microwave until just melted. Stir in the extra-virgin olive oil to combine and allow to cool slightly (so it doesn't melt the cheese when tossed).

combine seasoning

In a large bowl, combine the freshly grated Parmesan, truffle oil, chopped parsley, freshly ground black pepper, and fine sea or flaky salt.

toss fries

Add the hot drained fries to the bowl with the Parmesan mixture. Immediately pour the melted butter/olive oil over the fries and toss gently but thoroughly so the fries are evenly coated and the cheese adheres. Taste and adjust salt or truffle oil (adding up to an additional 1/2 tsp truffle oil if you want a stronger aroma).

finish and garnish

Transfer the tossed fries to a serving platter. Sprinkle the optional shaved Parmesan over the top and finish with a few extra pinches of flaky salt and a light grind of black pepper. Serve immediately while hot and crisp.

Dipping Sauce (optional)

Whisk together mayonnaise, minced garlic, lemon juice, 1/4 tsp salt, and 1/4 tsp black pepper in a small bowl. Refrigerate until ready to serve. Offer on the side for guests who like a creamy dip with the truffle parmesan fries.