Preheat oven to 450 degrees. Line two large baking sheets with parchment paper.
Add potatoes to a medium saucepan, cover with water and bring to a boil.
Reduce heat and cook on medium until potatoes are tender, about 20 minutes.
Drain and return potatoes to saucepan. Add butter and gently toss to coat. (You can put lid on pan, turn it upside down and toss this way or stir carefully with a wooden spoon.)
Transfer potatoes to prepared baking sheet, spreading out in a single layer. Using a heavy mug or glass, smash each potato to about 1/2 inch thickness.
Back for 20 minutes, remove from oven and turn with a spatula. Drizzle with olive oil and bake for 20 minutes more.
Once baked, sprinkle with vinegar, chives sea salt and pepper.
Serve hot with dinner or as a snack or appetizer.