Up to 3 days ahead: Wash and dry cranberries. Chop finely in a food processor. (One 12-ounce package of whole cranberries makes 2 cups finely chopped berries. Freeze the second cup for another use.) Combine cranberries and sugar in a small bowl. Cover mixture with plastic wrap and refrigerate. In a large bowl, dissolve gelatin in hot water. Add 1 cup reserved pineapple syrup. Mix well, refrigerate, and chill until partially set, about 1 hour. When gelatin is partially set, add cranberry mixture, pineapple, celery, and walnuts. Pour into a mold that has been lightly coated with cooking spray. Refrigerate and chill until firm.

1 day ahead: Divide grapes into small clusters. Dip clusters into beaten egg white, then roll in sugar to coat. Place on a paper-towel-lined plate and refrigerate.

Thanksgiving Day: Unmold salad on a large plate. Garnish with frosted grapes.