In a large pot, bring a couple inches of water to a boil, then insert steamer basket, add cauliflower to basket + steam about 15 minutes, until cauliflower is cooked through. Drain + set cauliflower aside.
In the same pot, melt the butter, then add garlic to sauté a minute or two.
Toss the garlic, butter + steamed cauliflower into a food processor + process until smooth.
Back in the pot, stir together cauliflower mixture, sour cream + parmesan. Add salt + pepper to taste, then garnish with chopped chives.