Remove the outer layers of the garlic bulb, keeping the cloves intact. Cut off the top of the bulb (about 1/4 inch) to expose the cloves. Drizzle with olive oil and wrap in aluminum foil.
Place the wrapped garlic bulb on a baking sheet and roast in the oven for about 30-35 minutes until the cloves are soft and caramelized.
Meanwhile, bring a large pot of salted water to a boil. Add the cauliflower florets and cook until tender, about 10-12 minutes.
Drain the cauliflower and return it to the pot.
Once the garlic is cool enough to handle, squeeze the roasted cloves out of their skins and add them to the pot with the cauliflower.
Add the butter, cream cheese, and milk to the cauliflower and garlic.
Use a potato masher or an immersion blender to blend everything until smooth and creamy.
Season with salt and pepper to taste. If the mixture is too thick, add more milk a tablespoon at a time until the desired consistency is reached.
Transfer the creamy mashed cauliflower to a serving bowl and sprinkle with chopped chives for garnish.
Notes
For a vegan version, substitute butter and cream cheese with plant-based alternatives.