Heat the oil in a large saucepan and fry the onion and celery for 10 mins, stirring occasionally until softened. If they start to catch, add a small splash of water. Add the garlic, thyme and 1/2 tsp black pepper and cook for 2 mins. Add the carrots, parsnips and stock and bring to the boil. Reduce to a simmer and cook for 20 mins until the vegetables are soft, stirring occasionally.

Blend using a stick blender until smooth. Add the cream and blitz again until combined, then taste for seasoning. To serve, ladle into bowls and scatter over a little chopped parsley, if you like.