For the black salsify soup with truffles, remove the skin from the black salsify, chop and sauté in the butter with the chopped shallots.
Add the chicken soup and cook until very soft with the lid closed. Puree with a hand blender, pass through a sieve, add cream and boil up again briefly. Season to taste with salt and a little pepper.
Arrange in soup cups or plates, slice truffle over it and serve the black salsify soup with truffle hot!