Cut potatoes into uniform 1/4-inch to 3/8-inch thick matchsticks. Leave skins on for rustic texture or peel if preferred.

Place cut potatoes into a large bowl filled with cold water and ice cubes. Let soak for at least 30 minutes (or up to 2 hours in the fridge) to draw out excess surface starch.

Preheat your oven to 425°F (220°C). Position two oven racks in the upper and lower thirds of the oven.

Drain potatoes thoroughly and spread them across a clean kitchen towel. Pat and rub vigorously with a second towel until every potato stick is bone dry.

Transfer dried potatoes to a large dry bowl. Sprinkle with cornstarch (if using) and toss to create a thin, invisible coating. Drizzle with oil and sprinkle with garlic powder, onion powder, paprika, and black pepper (reserve salt for after baking). Toss until evenly coated.

Arrange fries across two large rimmed baking sheets lined with parchment paper. Ensure fries are in a strict single layer with space between each stick; do not overlap or crowd.

Bake for 20 minutes. Remove pans from the oven, flip the fries using a thin spatula, and rotate the baking sheets between upper and lower racks.

Return to the oven and bake for an additional 15 to 20 minutes until deeply golden brown and crisp.

Transfer hot fries immediately to a large serving bowl, sprinkle generously with fine sea salt while still sizzling hot, toss well, and garnish with fresh parsley. Serve immediately.