In a bowl, combine gelatin with 5 cups boiling water; stir until completely dissolved. Stir in 2-1/2 quarts cold water. Refrigerate just until gelatin starts to mound.
In a blender container, place one-third of the gelatin mixture and 5-1/3 cups of the blueberries; blend until smooth. Pour into a bowl. Repeat two more times with remaining gelatin and blueberries.
Fold in whipped dessert topping. Scrape mixture into hotel pans or other shallow containers. Chill until firm, about 3 hours.
Spoon about 3/4 cup Blueberry Whip into each dessert glass. Garnish with a mint sprig, if desired.
Variation: Spoon alternate layers of Blueberry Whip and thawed and drained blueberries into dessert glasses using approximately 3/4 cup of the Blueberry Whip and 1/4 cup blueberries for each serving. Serve immediately. Garnish with mint sprigs, if desired.