Truffle & walnut soup

Serves 6 2 tbsp unsalted butter 1 garlic clove, peeled and chopped 1 onion, peeled and chopped 600g potatoes, peeled and chopped 600g celeriac, peeled and chopped 200g walnuts, finely chopped, plus halves to garnish 1 litre vegetable stock 4 tbsp truffle oil, plus extra to drizzle 2 tbsp fresh thyme leaves, plus sprigs to garnish 200ml double cream, plus 6 tsp to garnish sea salt and black pepper

In a large saucepan, melt the butter, then sauté the garlic and onion for 8-10 mins until softened. Stir in the potatoes, celeriac, walnuts and vegetable stock, and bring to the boil. Add the truffle oil and thyme leaves, and simmer, covered, for 20 mins until the potatoes and celeriac are soft. Mix in the double cream and season with salt and pepper.

Transfer the soup to a liquidiser and blend until very smooth. Divide between six bowls, add 1 tsp of cream to the top of each and mix in to create a pattern. Top with the thyme sprigs, crumble over the halved walnuts, drizzle with truffle oil, and serve.