Place cauliflower in a large pot and cover with water and 1/2 teaspoon salt. Boil until tender. Drain very well.
Place the cauliflower in a large pot, add minced garlic, sour cream and softened butter to the pot, and puree using a handheld blender until thick and smooth.
Serve warm topped with extra butter and chives, if you like.
Notes
Boil the cauliflower in salted water. This will help to add flavor to the dish right from the start.
Use an immersion blender to get the mashed cauliflower really smooth and creamy. You can use a potato masher and a hand whisk, but it will take a little more effort.