01 - Set oven temperature to 400°F and prepare for roasting garlic.
02 - Slice the garlic bulb's top to expose cloves, drizzle with olive oil, wrap in foil, and roast for 30-35 minutes until soft and golden. Allow to cool slightly.
03 - Steam cauliflower florets over boiling water for 12-15 minutes until tender. Drain and let stand to expel excess moisture.
04 - Squeeze the roasted garlic cloves from their skins into a food processor or large bowl.
05 - Add steamed cauliflower, butter, sour cream, milk, salt, and pepper to the roasted garlic. Blend or mash mixture until smooth and creamy.
06 - Adjust seasoning to taste, then fold in half of the chopped chives.
07 - Transfer the mashed cauliflower to a serving bowl and garnish with remaining chives.