Preheat to 400°F (200°C). Use an extra-large (15×21-inch) sheet pan or 2 smaller ones and use a pastry brush to spread 1/4 cup olive oil evenly over the pan(s). Set aside. Clean the potatoes; no need to peel.
To steam potatoes, see note 2. Boil potatoes: Bring a large pot of water to boil. Once boiling, add 1 tablespoon salt. Return water to boil, then add potatoes. Cook until potatoes can be pierced with a fork, about 20–25 minutes for baby potatoes or 25–30 for larger potatoes. Once potatoes are tender, drain and let stand in the colander to steam dry, about 5 minutes.
Place potatoes on a clean surface. Working 1 at a time, cover a potato with a clean kitchen towel. Apply pressure with your palm on top of the towel and potato. Smash the potato to the height of 1/2-inch and remove the towel. Use a metal spatula to gently scrape up the potato and transfer to the prepared pan. Repeat until all potatoes are smashed and on the pan, ensuring potatoes aren’t overlapping or too close together—they need room! Let smashed potatoes stand on the sheet pan to steam dry for 5 minutes.
Meanwhile, melt butter. Add seasonings to a small bowl—garlic powder, paprika, salt, and pepper (or to taste) and stir. Use the pastry brush to spread the melted butter evenly on the tops of all the potatoes. Sprinkle seasoning blend evenly on top of the potatoes, avoiding dropping seasonings on the pan (they’ll just burn).
Bake 35–45 minutes for baby potatoes and 45–55 minutes for larger potatoes or until potatoes are crispy and golden. Check potatoes a few times as you near the end of baking time to avoid burned potato 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! Smashed Potatoes don’t store well and aren’t great being made ahead of time.
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Notes
Note 1: I recommend baby Yukon gold/gold/Dutch yellow potatoes. I love the creamy, buttery flavor roasted Yukon golds deliver, and no need to peel beforehand. Do your best to get similarly sized potatoes, the smaller the better, as they cook more evenly and develop better crispy exteriors.Note 2: Steam instead of boil: Put cleaned potatoes in a large, microwave-safe bowl and fill with 1/2 inch water. Cover the bowl with plastic wrap and poke a few holes in the top. Microwave on high until potatoes are easily pierced with a fork. Check at 10 minutes, then continue for 5 minutes at a time, checking every 5 minutes. Add more water if needed. Once tender, remove potatoes, drain well, and let steam dry 5 minutes.Storage: To store leftover smashed potatoes, let them cool, then transfer to an airtight container. Refrigerate for up to 3 days. Reheat in the oven at 400°F until crispy, or use an air fryer for extra crunch.