Heat the oven to 220°C / 200°C (fan oven) / 425°F / Gas Mark 7: Line a baking sheet with parchment and set aside.

Wash and dry the potatoes: After washing, dry the potatoes as much as possible or leave them sitting out on the towel for a few minutes; the drier they are, the more crispy they get in the oven.

Slice each potato like an accordion: If using fingerlings, cut the larger ones in half so each piece is about an inch long. Hold the potato between your thumb and first finger. Use a sharp knife to cut thin slices into the potato, but stop just short of cutting all the way through. If you pinch the potato, you should see the slices open up.

Toss the potatoes with olive oil and salt: Drizzle 2 teaspoons of the olive oil over the potatoes, then sprinkle with salt. Use your hands or a spatula to mix until the potatoes are all evenly coated.

Roast for 15 minutes: Transfer the potatoes to the lined baking sheet and transfer to the oven to roast for 15 minutes.

After 15 minutes, the accordion slices in the potatoes will start to open up. Toss with the remaining 2 teaspoons of olive oil so that now some oil can get into the slices.

Continue roasting the potatoes until they are deeply golden and as crispy as you like them.

Cool briefly and then eat while warm and crispy.