Step 1

Combine potatoes, 1 cup vinegar and 1 tablespoon salt in a large saucepan over high heat

Step 2

Add water to cover potatoes by 1 inch

Step 3

Bring to a boil; cover and simmer until potatoes are just tender, 15 to 20 minutes

Step 4

Preheat oven to 450˚F

Step 5

Line a rimmed baking sheet with parchment paper

Step 6

Whisk 4 cups cold water and remaining 4 tablespoons salt in a large bowl until salt is dissolved

Step 7

Add 2 cups ice

Step 8

Using a slotted spoon, transfer cooked potatoes to ice water

Step 9

Let stand 30 seconds; drain and pat dry

Step 10

Allow potatoes to cool slightly

Step 11

Meanwhile, melt butter in a saucepan (or in a microwave) with pepper and 1 tablespoon chives

Step 12

Remove from heat and whisk in remaining 2 teaspoons vinegar

Step 13

Use the heel of your hand to gently smash and flatten each potato to a ½-inch thickness

Step 14

Arrange smashed potatoes in a single layer on prepared baking sheet

Step 15

Brush potatoes with butter mixture, and sprinkle generously with salt

Step 16

Flip and repeat on other side

Step 17

Bake until edges are crispy and golden, 30 to 40 minutes

Step 18

Brush generously with more vinegar; transfer to a serving platter

Step 19

Sprinkle with remaining 1 tablespoon chives and desired amount of salt

Step 20

Serve hot