Preheat to 400°F (200°C). Generously grease a (15×21-inch) sheet pan with cooking spray. Clean potatoes; no need to peel.
Bring 12 cups water to a boil. Add 1 tablespoon salt, then potatoes. Cook until easily pierced with a fork (20–25 minutes for baby potatoes, 25–30 for larger). Drain and let steam dry for 5 minutes.
Place potatoes on a clean surface. Working one at a time, cover each with a clean kitchen towel and press gently with the heel of your hand until about 1/2-inch thick. Use a metal spatula to gently to move them to the prepared pan, leaving space between each. Let steam dry on the pan for 5 minutes.
Melt butter. In a small bowl, mix garlic powder, paprika, salt, and pepper. Brush butter evenly over potatoes, then sprinkle with seasoning.
Roast for 25–45 minutes, until edges are crispy and golden (bigger potatoes will take longer). Check often to avoid burning on the bottoms. No need to flip the potatoes halfway.
Remove from oven and promptly grate on Parmesan cheese (if using) and sprinkle with fresh herbs. Serve immediately; these are best hot!
Whisk all sauce ingredients in a small bowl. Adjust to taste. Drizzle over potatoes or serve on the side.
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Notes
Note 1: Use Baby gold potatoes for their creamy, buttery flavor and thin skins. Use similar sizes so they cook evenly. Smaller potatoes crisp up better.Storage: Best fresh, but if you have leftovers, cool completely, then store in an airtight container in the fridge for up to 3 days. Reheat in a 400°F oven or air fryer until crispy.