Place cauliflower in 4-quart saucepan; cover with water. Cover; heat to boiling. Reduce heat and simmer cauliflower 10 to 12 minutes or until very tender. Drain. Puree cauliflower with sour cream with immersion blender or in batches in food processor until smooth and creamy. Stir in 3/4 cup cheese, 1/4 cup chives, 1/4 cup bacon, salt and pepper. Return to saucepan; heat over low heat, stirring constantly until cheese is melted and mixture is heated through. Spoon into serving dish. Top with remaining cheese, chives and bacon.