Use small red potatoes, measuring 1 to 2 inches in diameter. If you prefer to use kosher salt, you will need 1½ cups of Morton kosher salt or 2½ cups of Diamond Crystal. Cider vinegar works here, too.
6 tablespoons olive oil
2 pounds small red potatoes
1 1/4 cups salt
3 tablespoons malt vinegar
1. Adjust oven rack to upper-middle position and heat oven to 500 degrees. Set wire rack inside rimmed baking sheet. Brush second rimmed baking sheet evenly with oil. Bring 2 quarts water to boil in Dutch oven over medium-high heat. Stir in potatoes and salt, and cook until just tender and paring knife slips easily in and out of potatoes, 20 to 30 minutes. Drain potatoes and transfer to wire rack; let dry for 10 minutes.
2. Transfer potatoes to oiled baking sheet. Flatten each potato with underside of measuring cup until ½ inch thick. Brush potatoes with half of vinegar and season with pepper. Roast until potatoes are well browned, 25 to 30 minutes. Brush with remaining vinegar. Transfer potatoes to platter, smashed side up. Serve.