Preheat the oven to 220°C / 425°F / 200°C fan
Peel the potatoes if desired, then cut into even chunks
Parboil the potatoes in salted water for 8 to 10 minutes
Drain well and let them steam dry for a few minutes
Shake the potatoes in the colander to rough up the edges
Put roasting oil or fat in a roasting tray and heat it in the oven
Carefully add the potatoes to the hot tray
Turn the potatoes to coat them in the oil or fat
Season with salt and pepper
Roast for 40 to 50 minutes, turning once or twice
Roast until golden and crisp on the outside and soft inside
Serve immediately