Cook the cauliflower any way you like. You can boil, steam or microwave. Whatever works.
Using a cheesecloth or two colanders that fit inside each other, wring or press out as much liquid as you can from the cauliflower. The more water you get out of them, the more their consistency will be like mashed potatoes.
Transfer the drained cauliflower to a food processor (or a bowl/pot if you have a stick blender) and blend with the other ingredients until well combined.
Serve with an extra pat of butter.
Notes
Please note that the nutrition data below is a ballpark figure. Exact data is not possible.