Heat the air fryer to 180°C/350°F. Toss the squash in the oil and roast in the air fryer for 20 mins, shaking the drawer halfway through. Vou may need to do this
in two batches. Meanwhile, heat the remaining oil in a large pan. Add the on ion and fry gently for 5 mins, to soften. Add the ground coriander and cook for 1-2 mins. When the squash is tender, add it to the anions, along with the sweet potatoes and pour in the vegetable stock. Bring to the bail and simmer for 15 mins, until the vegetables are tender.
Pour the soup, in batches, into a blender and whizz until smooth.
(Vou can prepare this a couple of days in advance, and chill in an airtight container or freeze it.)
To serve, warm the soup through thoroughly, swirl in the soured cream and add a sprinkling of crushed pink peppercorns.