Preheat oven to 400°F. Cut phyllo dough crosswise into 4 pieces. Place 1 sheet phyllo dough on work surface. Keep remaining sheets covered with plastic wrap and damp kitchen towel. Lightly coat first sheet with cooking spray; place in large custard cup. Place second sheet on top of first, alternating corners; spray with cooking spray. Repeat with remaining 2 phyllo sheets, continuing to alternate corners. Repeat with remaining phyllo dough to form 6 strudel cups. Place custard cups on cookie sheet; bake about 15 minutes or until pastry is golden. Let cool to room temperature.

Meanwhile, combine blackberries and sugar in small bowl; let stand 15 minutes. Mix whipped topping and yogurt in medium bowl. Reserve 1/2 cup blackberries for garnish; gently stir remaining blackberries into whipped topping mixture. Spoon into cooled pastry cups. Garnish with reserved blackberries and mint sprigs.