Melt butter over medium heat in a large heavy pot. Add
the onion and sauté until tender, but not brown, which
should take 6 minutes. Add the cauliflower and sauté for
2 minutes or lightly brown. Add the chicken stock and
simmer until the cauliflower is tender, about 25 minutes.
Purée the soup until smooth. Season to taste with salt
and pepper then ladle into bowls. Drizzle with truffle oil,
sprinkle with medium curry, chives and serve.