Wash and scrub the potatoes. If using peeled, peel them; otherwise leave skins on. Cut potatoes into 1/4–1/3-inch sticks for classic shoestring-style truffle fries or into 1/2-inch for thicker fries. Rinse the cut fries under cold water until water runs clear to remove excess surface starch.

Soak the cut fries in a large bowl of cold water for at least 30 minutes, or up to 2 hours in the refrigerator. This step improves crispness by removing more starch.

Drain the fries and spread them on a clean kitchen towel or paper towels. Pat thoroughly dry; any surface moisture will cause oil to splatter and reduce crispness.

First fry (blanch)

Heat 1 to 1 1/2 cups of oil in a heavy-bottomed pot or deep fryer to 300°F (150°C). If you don't have a thermometer, heat until oil shimmers but does not smoke. Fry potatoes in small batches for 4–6 minutes until they are just cooked through but not browned (soft and pale). Remove with a slotted spoon to a wire rack or paper towel-lined tray to drain. Let cool 10–15 minutes.

Second fry (crisp)

Increase oil temperature to 375–380°F (190–195°C). Return the blanched fries in batches and fry until golden and crisp, about 2–4 minutes depending on thickness. Work quickly to avoid lowering oil temperature too much between batches. Drain on a wire rack or a paper towel-lined tray and immediately sprinkle with the measured sea salt while still hot so the salt adheres.

Truffle-seasoning & assembly

While the fries are finishing the second fry, melt the unsalted butter in a small saucepan over low heat or in a microwave until just melted — do not brown the butter. Remove from heat.

Stir the truffle oil into the melted butter until combined. Use measured truffle oil sparingly (1 tsp) because it is highly aromatic; you can add up to 1/2 tsp more to intensify if desired, but avoid overpowering the fries.

Place the hot, drained fries in a large mixing bowl. Immediately pour the warm truffle-butter mixture over the fries and toss gently but thoroughly to coat. The warmth helps the butter and truffle oil adhere.

Sprinkle the grated Parmesan, optional Pecorino, chopped parsley, and freshly ground black pepper over the fries. Gently toss again to distribute evenly. Taste and adjust salt if needed (remember Parmesan is salty).

Serve the truffle fries immediately while hot and crisp for best texture and aroma.

Dipping sauce (optional)

While fries are frying, mix mayonnaise, grated garlic, lemon juice, salt, and black pepper in a small bowl until combined. Taste and adjust seasoning. Chill briefly or serve at room temperature alongside the fries.