Heat half the oil in a large saucepan over a medium-low heat. Sweat the onion, celery and garlic with the pan partially covered by the lid for 15 mins, until softened. Tip in the celeriac and pour over the stock. Bring to a simmer, cover, and cook for 15-20 mins, until the celeriac is tender. Remove from the heat, stir in the nutmeg, crème fraîche and some seasoning. Blitz with a hand blender until smooth.

Meanwhile, heat the remaining oil in a frying pan over a medium heat. Fry the hazelnuts and breadcrumbs gently for a few minutes, until toasted. Put in a bowl, stir in the chives and season. Ladle the soup into bowls and spoon over the hazelnut crumble to serve.