Using celeriac with traditional potato gives this soup a velvety, creamy texture.
Equipment and preparation: For this recipe you will need a blender.
To make the stock, put the grated carrot, onion, celery and garlic into a large heatproof bowl. Add a pinch of salt and pepper and pour over 1 litre/1¾ pints of boiling water. Set aside to steep for 10-15 minutes while you prepare the soup.
Heat a large heavy-based saucepan or casserole dish over a medium heat. Add a dash of oil and, once hot, add the onion, potatoes, celeriac and thyme leaves. Cook over a medium heat for 10 minutes, or until the vegetables have softened.
Strain the stock through a sieve into the pan of celeriac. Simmer gently for 10-15 minutes until the celeriac is nearly tender.
Add the leeks, cover the pan and cook for a further 5-7 minutes, or until the leeks are wilted and tender but still bright green.
Remove from the heat and blend in batches until really smooth. (Blend for a minute or longer for a really velvety texture.) The soup can be stored in the fridge or frozen at this stage.
Transfer the blended soup to a clean pan. Reheat the soup if necessary, taste and season with salt and pepper to taste.To serve, spoon into bowls and garnish with chopped chives.