People either really love cauliflower or they really don't. Those of us in the first camp will enjoy it almost any way - raw, steamed with butter and lemon, or in this case puréed.
Place roughly chopped cauliflower in a medium saucepan, add stock. Bring to a boil and reduce heat to a simmer. Cover and cook until the cauliflower is tender, about 10 minutes.
Purée cooked cauliflower in blender:
Place the cooked cauliflower in a blender. Add a couple tablespoons or more of the cooking liquid and pulse until smooth, about 15 to 20 seconds.
Add the sour cream and butter, and blend 5 to 10 seconds more. Season to taste with salt and pepper.
Recipe barely adapted from Martha Stewart Living.