STEP 1

In a large saucepan, heat the oil over a low heat. Tie the thyme sprigs and bay leaves together with a piece of string and add them to the pan with the onion and a pinch of salt. Cook for about 10 mins until softened but not coloured.

STEP 2

Stir in the garlic and cook for 1 min more, then tip in the celeriac and potato. Give everything a good stir and season with a big pinch of salt and white pepper. Pour in the stock, bring to the boil, then simmer for around 30 mins until the vegetables are completely soft.

STEP 3

Discard the herbs, then stir through the cream, remove from the heat and blitz until completely smooth. Stir through 1/2 tbsp truffle oil at a time and taste for seasoning – the strength of the oil will vary, so it’s better to start with less oil and add a little at a time.

STEP 4

To serve, reheat the soup until piping hot, then ladle into bowls and top with the hazelnuts, some black pepper and an extra drizzle of truffle oil.