Bring two cups of water to a boil in a large simmering pot.
Place cauliflower in boiling water and cook for approximately 15 minutes, or until very soft.
Drain your cauliflower using a strainer, place it back in the pot, and add the milk, butter, sour cream, garlic salt, and black pepper.
Mix all ingredients until the texture is creamy - do not over mash. I prefer using a hand-held blender to create a creamy texture but feel free to use a masher if you don’t have an electric one.
Once you're finished mashing, garnish with chives and serve.