Peel the potatoes. Cut into 1 cm (1/3-inch)-thick batonnets and add to a bowl with cold water. Let them soak in cold water for about 30 minutes. Note: Soaking them in water removes the excess starches, improving crispiness and promoting even cooking. When I’m in a rush and making these for a casual family dinner, I skip this step but they really do come out better if you soak them in water for 30 minutes. At the very least, rinse them well in cold water.
Drain the potatoes (rinsing them with clean cold water) and dry them well with a clean kitchen towel.
Toss the potatoes with oil, salt, and garlic powder.
Preheat the air fryer to 380°F/ 190°C for 3 minutes.
Add the potatoes (in one layer) to the air fryer. Air fry until cooked, shaking the basket every 5 minutes. For 1/3-inch fries at 380°F/ 190°C it takes about 15 minutes (more or less depending on your air fryer/basket size/how full the basket is).
Toss the cooked fries with black pepper, thyme, parmesan, and, optionally, more salt to taste (if needed).