Scrub and peel the potatoes and cut them into large even-sized chunks.
Ensure you rinse the potatoes under cold running water. This is to remove the excess starch from the potatoes.
In lightly salted boiling water, par boil your potatoes for 10 minutes.
Once par boiled drain them and coat in the fat of your choice. Putting the potatoes into hot oil or fat will mean they will soak up less fat and will crisp better. Season well.
For extra crispy potatoes, either score the outside of the potato with a fork after par boiling or shake the pan to roughen up the outside.
Pop the potatoes in a roasting tin and add to a pre-heated oven on 200°C/425°F/Gas mark 6, for approximately 45 minutes. Make sure you turn them at least twice.