1.Place potatoes in a large saucepan in a single layer. Add vinegar, water and salt; bring to the boil.
2.Boil, partially covered, for 15 minutes or until potatoes are tender. Drain.
3.Meanwhile, preheat oven to 220°C (200°C fan-forced). Transfer potatoes to a large oven tray lined with baking paper.
4.Using a potato masher or fork, press potatoes until flattened slightly.
5.Drizzle with ½ cup extra virgin olive oil. Roast potatoes for 30 minutes or until golden and crisp. Season to taste; serve.
Roast potatoes should be finished just before serving to retain their crunch. If too pale, brush generously with melted butter. Turn oven to hottest temperature; roast 10 minutes or until browned and crisp while meat or poultry rests. For potato perfection next time, roast in duck fat or use a shallower pan.