Serves 8 as an hors d'oeuvre.

If using fromage blanc, in a bowl stir together with milk and Sherry until smooth. If using cream cheese, with an electric mixer beat together with
milk and Sherry until smooth. Crumble Roquefort and gently stir into
mixture (being careful not to break up lumps). Dip may be made 1 day
ahead and chilled, covered.
Have ready a large bowl of ice and cold water. Trim the root ends of
endives and separate leaves. Trim celery to 4- to 6-inch lengths. Remove
any discolored outer leaves from radicchio and trim root end slightly so
radicchio stands upright. Put vegetables in bowl of ice water to crisp
(and to help radicchio leaves open). Let vegetables stand at least 15
minutes and up to 2 hours.
In a colander drain radicchio and shake to remove water. Twist and pull
out center leaves to form a "bowl" for dip. Spoon dip into radicchio or a
small bowl.
In colander drain endive and celery and pat dry. Quarter the apple and
remove core. Cut quarters into thin wedges. Put several ice cubes in each
of 2 wine glasses and stand endive, celery, and apple over ice.
Serve dip with apple, endive, and celery.