Wash and peel potatoes if desired (skins can be left on for texture). Cut each potato into 1/3 inch (8 mm) sticks for uniform fries. Place cut fries in a large bowl of cold water and soak 30 minutes (or up to 2 hours) to remove excess starch.

Rinse and dry

Drain the soaking water and rinse the potatoes under cold running water until water runs clear. Spread fries on a clean kitchen towel or paper towels and dry thoroughly—patting is important to avoid oil splatter and to get crispness.

Par-cook (optional oven method)

Preheat oven to 425°F (220°C). Toss dried fries with olive oil, 1 tsp sea salt, 1/4 tsp black pepper and garlic powder on a rimmed baking sheet in a single layer. Roast 18–22 minutes, flipping once, until edges are light golden and interiors tender. Proceed to step 'Final crisp' to finish and cheese. (If you prefer deep-frying crispy fries, skip this oven method and follow the frying steps below.)

Deep-fry method - heat oil

If deep-frying: pour vegetable oil into a deep heavy pot or deep-fryer to a depth of about 2–3 inches (enough to submerge fries) and heat to 325°F (160°C). Use a thermometer to maintain temperature.

First fry (blanch)

Fry the fries in small batches for 4–5 minutes until soft but not colored. Remove with a slotted spoon to a wire rack or paper towel-lined tray to drain. Increase oil temperature to 375°F (190°C) for the final crisp.

Final crisp

Fry blanched fries again in batches at 375°F (190°C) for 2–3 minutes until golden and crisp. If using the oven-par-cook method, place roasted fries under a high broil for 1–2 minutes per side or bake at 450°F (230°C) for 5–7 minutes to crisp. Transfer fries to a large mixing bowl while hot.

Season and cheese

Immediately toss the hot fries with the remaining 1/2 tsp sea salt (adjust to taste), 1/4 tsp black pepper, and the grated Parmesan. Use tongs to gently toss so cheese lightly adheres and begins to melt from residual heat. Sprinkle chopped parsley over fries and toss once more.

Serve

Transfer to a serving platter. Serve immediately with the Truffle Chive Dipping Sauce on the side so fries remain crisp.

Truffle Chive Dipping Sauce

Combine mayonnaise and sour cream in a small bowl and whisk until smooth.

Stir in finely chopped chives, lemon juice, minced garlic, truffle oil, salt and pepper. Taste and adjust seasoning — add a few more drops of truffle oil if you want a stronger truffle note, but add sparingly as it is potent.

Cover and refrigerate at least 15 minutes for flavors to meld. Bring to room temperature for 10 minutes before serving if chilled very cold.

Give the sauce a final stir, then transfer to a small serving bowl alongside the hot Parm Fries.