Jerusalem artichokes have a wonderful texture, with an earthy, slightly nutty flavour. Here they blend perfectly with the luxury of the white truffle oil.
Melt the butter in a saucepan, add the onions and a pinch of salt and cook gently until soft, without colouring. Add 250ml/9fl oz water, the chicken stock, artichokes and bouquet garni and bring to the boil. Cook for about 20 minutes. Once the artichokes are soft, remove the bouquet garni. Transfer to a blender and blend to a fine purée, then pass through a fine sieve.
Whisk the butter into the soup, add a few drops of white truffle oil and some truffle juice (if using), then season with salt and pepper.
Serve with a sprinkling of fresh chives.
