Eating healthily doesn’t mean you have to cut out your favourite dishes. By cooking these chips in the oven you dramatically reduce the amount of oil used. Vary the taste with your own choice of herbs and spices.
Preheat the oven to 220C/425F/Gas 7. Cut the sweet potatoes into thick wedges and put into a large mixing bowl. Cut the white potatoes into slightly thinner wedges (they take longer to cook so need to be slightly smaller for an equal cooking time) and add to the bowl. Add the remaining ingredients and toss until the wedges are evenly coated. Season with sea salt then spread over a non-stick baking tray in an even layer. (Put the sweet potatoes in the centre and the white potatoes round the edge of the tray where it will be hotter.)
Cook for 20-25 minutes, checking after 10 minutes, shaking and turning occasionally, until cooked through. If the sweet potatoes are cooked before the others are ready then remove them from the oven and leave the rest to cook for longer.