Slice the russet potatoes into thin fries, about 1/4-inch thick. Try to keep the fries similar in size so they cook evenly.
Place the cut potatoes in a large bowl of cold water and soak for at least 20–30 minutes to remove excess starch for crispier fries.
Drain the potatoes and dry them extremely well with paper towels or a clean kitchen towel. Moisture prevents the fries from crisping properly.
Preheat the air fryer to 380°F if your air fryer requires preheating.
Add the potatoes to a large bowl and toss with olive oil, salt, and black pepper until evenly coated.
Arrange the fries in the air fryer basket in a mostly even layer, working in batches if needed to avoid overcrowding.
Air fry for 18–24 minutes, shaking the basket halfway through cooking, until the fries are deeply golden and crispy on the outside.
While the fries cook, stir together the melted butter and grated garlic in a large mixing bowl.
Immediately add the hot fries to the bowl with the garlic butter and toss well to coat.
Sprinkle in the finely grated parmesan cheese and parsley or chives, tossing again so the cheese evenly coats the fries.
Finish with truffle oil and toss lightly one final time. Start with 1 tsp truffle oil and add more to taste if desired. Sprinkle with flaky salt and optional French seasoning before serving. Serve immediately with garlic aioli or lemon wedges if desired.