Cut potatoes into even-sized pieces. Place into a large saucepan and cover with cold water. Bring to the boil and cook for 5 minutes or until just tender but not cooked through. Drain well and roughen the surface by returning to the pan and giving them a good shake.
Toss with oil or duck fat, rosemary leaves and season well with sea salt flakes and cracked black pepper. Place the potatoes into a roasting pan in a single layer. Cook in a preheated oven at 200°C for 45-60 minutes or until crisp and golden, turning occasionally. Serve.
