Step 1

Bring 1 inch of water to a simmer in a large pot fitted with a steamer basket. Add cauliflower, cover and cook until tender, 15 to 20 minutes.

Step 2

Remove the cauliflower and basket; drain the excess water. Return the cauliflower to the pot over low heat and mash with a fork or potato masher. Add cheese, sour cream, horseradish, butter, season with salt and pepper and mash until smooth. Stir in chives. Garnish with more chives, if desired.