Place the potatoes in a saucepan of cold lightly-salted water and bring to the boil.
Reduce the heat to medium and cook for a further 5 minutes, or until partly cooked.
Drain and return the potatoes to the pan.
Lightly fry the potatoes (without oil) over medium heat to dry them out, and to rough up their edges. Set aside.
Place the Ducko duck fat in a roasting pan and heat it in the oven for 5 minutes.
Remove the pan from the oven and carefully add the potatoes to the Ducko duck fat. Gently toss or shake the roasting pan to ensure you coat all the potatoes with the Ducko duck fat.
Return the pan to the oven and roast the potatoes for 45 minutes, or until golden and crisp. Turn the potatoes every 15-minutes to ensure it is nice and golden on all its sides.