Preheat your oven to 425 degrees Fahrenheit (220 degrees Celsius). Line a large baking sheet with parchment paper.
Place the potato chunks in a large bowl. Cover them completely with cold water and let them soak for at least 30 minutes. This removes surface starch, which helps create a crispier exterior.
Drain the potatoes thoroughly and pat them completely dry using paper towels. Moisture prevents crisping.
Toss the dried potatoes with olive oil, salt, pepper, and garlic powder until evenly coated.
Spread the potatoes in a single layer on the prepared baking sheet. Do not overcrowd the pan; use two sheets if necessary.
Roast for 25 minutes.
Remove the pan from the oven. Sprinkle the grated Parmesan cheese evenly over the potatoes. Gently toss them on the pan.
Return the potatoes to the oven and roast for another 10 to 15 minutes, or until the cheese is melted, golden brown, and the potatoes are very crisp.
Remove from the oven, sprinkle with fresh parsley, and serve immediately.
Notes
For extra crunch, toss the potatoes with 1 teaspoon of cornstarch along with the oil and seasonings before the first roast.
Ensure your oven temperature is accurate; high heat is key to crispiness.
Use finely grated Parmesan for the best melting and crust formation.