Place the cauliflower and water or broth in a medium saucepan, bring to a boil over high heat. When it starts to boil, reduce the heat and cook until the cauliflower is tender, about 10 minutes. Place the cauliflower in the blender. Add a few tablespoons of the cooking liquid and mix until smooth. Add the cream and butter and mix until smooth. Season with salt and pepper. Serve it hot.