Step 1

Preheat the oven to 425 degrees F. Fit a wire rack in a sheet pan.

Step 2

Add the potatoes to a large pot and cover with cold water by at least 1 inch. Heavily salt the water and bring to a boil over high heat. Continue to boil until the potatoes can be easily smashed with the back of a spoon, about 10 minutes. Drain the potatoes in a colander, then shake the colander as hard as you can without losing any of the potatoes until they are roughed up and craggy. Transfer the potatoes to the prepared sheet pan and let dry for 10 minutes. Meanwhile, pour the vegetable oil onto a separate sheet pan and heat in the oven for 10 minutes.

Step 3

Carefully remove the sheet pan from the oven and transfer the potatoes to the hot oil (carefully, as the oil might splatter a bit). Gently mash the potatoes with the back of a spoon until they fill most of the sheet pan, then season with 1 tablespoon salt and a few grinds of pepper. Scatter the butter over top of the potatoes.

Step 4

Bake until the bottoms of the potatoes are turning golden brown, about 45 minutes. Toss the potatoes and continue to bake until the bottoms are golden brown and the tops are golden brown in a few places, another 50 to 55 minutes.

Step 5

Let cool slightly, about 10 minutes. Season with salt and pepper and sprinkle with the chives.