Prepare: Sauté 3/4 of the cauliflower and potatoes in butter. Extinguish with consomme, simmer on low heat with lid closed until soft. Now grind.
Just before serving: Bring soup to a boil, add milk or cream while stirring gently with a hand mixer (cutting knife). Blend until the soup is creamy. Season vigorously with salt and freshly ground pepper.
Serve: Arrange in heated plates or cups. Finely shave truffles and/or remaining cauliflower on top. Serve immediately.