Place 1 sheet of phyllo on a work surface. (Cover remaining sheets to prevent them from drying out.) Lightly coat phyllo sheet with cooking spray. Top with another sheet of phyllo; coat with cooking spray. Lightly sprinkle with some of the coarse sugar. Repeat layering with remaining phyllo sheets, cooking spray, and coarse sugar, coating each sheet with cooking spray and sprinkling every other sheet with some of the coarse sugar. Cut the stack crosswise into six even strips. Cut each strip crosswise into three 2x3-inch rectangles (you should have 18 rectangles). Place all of the stacks on ungreased cookie sheets. (There will be 2 extra phyllo stacks to use in case any break.) Bake in a 350 degree F oven for 10 to 12 minutes or until golden. Remove and cool on wire racks.
For blueberry curd, combine 1-1/2 cups blueberries, the orange juice, and orange peel in a medium saucepan. Bring to boiling; reduce heat. Simmer, covered, for 5 minutes. Remove from heat; cool slightly (about 10 minutes). Transfer blueberry mixture to a blender or food processor. Cover and blend or process until smooth. Return to saucepan. Stir in 2 tablespoons sugar and the butter.
In a small bowl combine the cornstarch and 2 teaspoons cold water. Add to blueberry mixture in saucepan. Cook and stir over medium heat until thickened and bubbly. Cook and stir 2 minutes more. Remove from heat; transfer to a bowl. Cover surface with plastic wrap and chill for 2 hours or overnight.
To serve, stir together 1 tablespoon of the blueberry curd and 1 teaspoon water in a small bowl; set aside. Divide remaining blueberry curd in half. Place 1 phyllo stack on each of 8 dessert plates. Spoon half of the blueberry curd evenly atop phyllo stacks. Spoon 1/4 cup fruit atop each stack. Spoon remaining half of blueberry curd evenly atop fruit. Top each stack with another phyllo stack. Top each dessert with some of the whipped topping. Drizzle with the reserved blueberry curd mixture. If desired, garnish with mint sprigs. Makes 8 servings.