To make roasties in an air fryer, peel 1kg Maris Piper potatoes and cut into walnut-sized chunks. Soak in a large pan of salted water for 1 hr. Drain and rinse, then pat dry with kitchen paper and tip into a bowl with 2 tsp vegetable oil. Toss to coat. Arrange the potatoes in a single layer in the air fryer basket (you may need to do this in batches) and cook on 180C for 20 mins. Turn or shake the potatoes, then cook for another 10 mins, still at 180C. Check the potatoes – if you want them crispier, cook for a further 10-15 mins, checking every 5 mins. If you have to cook in batches, add the previous batches together for the final 5 mins. You will get a better result if you cook in a single layer, but cooking in batches does use more energy – you can cook the potatoes in more than one layer, but you’ll need to cook them for longer to make sure they’re crisp. Keep moving them around every 10 mins to help achieve this. Remove the potatoes from the basket as soon as they’re ready so the skin doesn’t soften in the steam.

Instead of boiling the potatoes, you can microwave them. Tip the potatoes into a large heatproof bowl, pour over 100ml water, cover with a plate and microwave on high for 25-30 mins, turning occasionally  until evenly soft and fluffy. Drain well before roasting.