Cut the potatoes into evenly sized pieces, ensuring they're not too big. Steam for 5 mins in a steamer insert set over a pan of boiling water, or simmer gently for 5 mins. Drain well.

Tip the drained potatoes into the bottom of an air fryer. Add the oil and toss everything together to ensure the potatoes are well-coated. Set the fryer to cook at 190°C for 30 mins using the paddle. Check the potatoes are cooked through, then cook for another 5-10 mins if they're not tender or brown enough. Season well.