Preheat the oven to 400°F (200°C). Trim the cauliflower and divide into smaller florets. Place in a large baking dish.
Slice the butter thinly and cover the florets. Bake in the oven for 30 minutes.
Turn the florets and baste in butter. Roast for another 15 minutes or until the cauliflower has turned slightly golden.
Remove and pour into a pan. Let boil for 15 minutes, until the cauliflower is soft.
Blend with an immersion blender. Season with salt and pepper to taste.
Serve as a side dish to fish, meat, or poultry.