Steam the cauliflower by bringing a couple of inches of water to a boil in a stockpot. Put chopped cauliflower in a steamer basket and set in pot. Cover the pan and steam for 8-10 minutes until cauliflower is very soft.
Drain cauliflower and put on a paper towel lined plate. Let sit for 5-10 minutes and then squeeze all moisture out by blotting with additional paper towels (THIS IS VERY IMPORTANT - IF THE CAULIFLOWER IS TOO WET, YOUR MASH WILL BE SOUPY).
Mix cauliflower with heavy cream, sour cream and butter and either mash using a food processor/blender, or immersion blender.
Once mashed to desired consistency, put back in pan and reheat over medium heat until warmed.
Add the Parmesan and chives and mix well. Salt/pepper, to taste. Serve immediately.
Nutrition Info Per Serving: Calories 116 Total Fat 11 g Cholesterol 30 mg Sodium 140 mg Potassium 158 mg Total Carbohydrate 3 g Dietary Fiber 1 g Sugars 1 g Protein 3 g