Strawberry Chiffon Dessert

Line bottom of a 9- or 9 1/2-inch tart pan with a removable bottom or a 9-inch springform pan with parchment paper; set aside.
In a blender or food processor, blend or process the 3 cups strawberries until smooth.
Measure 1 3/4 cups of the pureed strawberries (puree additional strawberries if needed to measure 1 3/4 cups).
In a medium saucepan, combine sugar (if using) and gelatin.
Stir in the pureed strawberries; let stand for 5 minutes to soften gelatin.
Cook and stir over medium heat until the mixture bubbles and the gelatin is dissolved.
Gradually stir about half of the gelatin mixture into the egg whites.
Return all of the mixture to the saucepan.
Cook, stirring constantly, over low heat for 2 to 3 minutes or until slightly thickened.
Do not boil.
Strain mixture into a medium bowl.
Stir in sugar substitute (if using).
Chill for 1 1/2 to 2 hours or just until the mixture mounds when dropped from a spoon, stirring occasionally.
Meanwhile, cut about half of the split ladyfingers in half crosswise; stand these on end around the outside edge of prepared pan.
Arrange the remaining split ladyfingers in bottom of pan (ladyfingers may not completely cover bottom of pan).
Slowly drizzle the orange juice over the ladyfingers.
Fold whipped topping into strawberry mixture; spread into the ladyfinger-lined pan.
Cover and chill about 2 hours or until set.
To serve, if desired, garnish with additional berries and mint leaves.