In a food processor, puree the blue and cream cheeses until very smooth. Season with salt and pepper, to taste. Fold the whipped cream into the mousse until well blended. There should be no lumps. Transfer the mousse to a pastry bag fitted with a round tip. Pipe the mousse onto the white bread rounds and top each with a radish slice. Serve.
Recipe courtesy of Garde Manger, John Wiley and Sons, Inc., 2000