Place 1/2 cup of the raspberries, superfine sugar and water in a small saucepan; cover and, over low heat, cook until the sugar dissolves.
Stir occasionally and continue to cook another 10 minutes, until berries are soft; uncover and cook 1 minute; remove from heat and cool completely.
Puree all the contents of the saucepan and sieve to remove seeds; chill, covered, 6-8 hours.
(If desired, whip the heavy cream until it begins to mound; add confectioners' sugar and vanilla and beat until firm peaks form).
Pour the raspberry puree into a bowl and stir 1/4 cup of whatever cream is being used into the puree; fold in the remaining cream and remaining raspberries.
Spoon fool into flutes, goblets or parfait dishes and chill at least 1 hour before serving.
Variations: Apricot Fool: Puree 1/2 pound fresh apricots, (peeled by dipping in boiled water and pitted) with 1/2 T superfine sugar; fold all of the puree into all of the whipped cream in one step; chill and serve.
Blackberry Fool: Simmer 3/4 cup blackberries with2 1/2 T superfine sugar, or more to taste; fold all of the simmered and chilled puree into all of the whipped cream in one step; chill and serve.
Peach or Nectarine Fool: Puree 2 medium peaches (peeled by dipping in boiling water, pitted and cut in chunks), uncooked, with 1 1/2 T superfine sugar; fold all of the puree into all the whipped cream in one step; chill and serve.
Strawberry Fool: Puree 1/2 cup uncooked strawberries with 1 1/2 T superfine sugar; strain though mesh sieve; fold all the puree into all the whipped cream in one step; chill and serve.