The potatoes don’t roast in this oil, so much as braise: they will crisp up in parts, but mostly just become softened and rich in the sweet peppery juices. Preheat the oven to 220C/200C Fan/Gas 7.
Drizzle any remaining oil over the potatoes and bake for 40 minutes. Take the tray out of the oven and dot each of the potatoes with a little butter, then bake for a further 10 minutes ...