Cover whole duck with water in large stock pot. Add salt, and bring to a boil. Skim off foam.
Place celery, parsley, allspice, and cloves in a cheese cloth bag, and add to stock pot. Cover and cook over low heat until meat is tender, approximately 1 1/2 hours.
Remove cheese cloth bag from stock pot. Remove duck. Discard bones, cut up meat, and return to the broth.
Mix in prunes, raisins and apple. Simmer for 30 minutes.
In a medium bowl, beat flour and sugar into cream until smooth. Beat in duck blood gradually. Add 1/2 cup hot soup stock to blood mixture, blending thoroughly. Pour mixture slowly back into stock pot, stirring constantly until soup comes to a boil. Season to taste with salt, pepper, lemon juice and vinegar.
