Crème Dubarry, or Cauliflower Soup

Classically, a crème Dubarry would be thickened with a béchamel sauce and a potage Dubarry with potatoes. I prefer to use rice, partly for convenience but also for the aerated and ‘moussey’ texture that can be achieved in a blender. If you do not have a blender, it might be better to use potatoes (300 g/10½ oz