Preparation

• Arrange 2 racks to divide the oven into thirds and heat to 425°F. Meanwhile, bring the water to a boil in a large pot over medium-high heat. Prepare an ice water bath by filling a large bowl with ice and water; set aside.
• You can peel the potatoes if desired, but the skins add texture and flavor to the fries. Cut the potatoes lengthwise into ¼-inch-thick planks. Stack 2 of these planks on top of each other, then cut lengthwise into ¼-inch-thick sticks or batons.
• Add ¼ of the potatoes to the boiling water and cook for 2 minutes. Using tongs or a slotted spoon, transfer the blanched potatoes to the ice water bath to shock the potatoes and halt the cooking process. Continue blanching and shocking potatoes in 3 more batches.
• Remove the chilled potatoes from the ice bath and spread them into a single layer on paper towels or a clean kitchen towel. Pat completely dry with more paper towels or another kitchen towel. Transfer to a large bowl.
• Mix the Parmesan, salt, and garlic powder together in a small bowl. Drizzle the oil over the potatoes and toss to coat. Sprinkle the Parmesan mixture over the fries and toss again until evenly coated.
• Coat 2 rimmed baking sheets with cooking spray. Transfer the fries to the baking sheets and arrange in a single layer. Bake, flipping the fries halfway through, until golden-brown, 25 to 28 minutes. Transfer the fries to a serving bowl, sprinkle with parsley, and serve hot with ketchup if desired.