Step 1

In a medium saucepan over medium heat, whisk together raspberry and strawberry juices with 2/3 cup sugar and cornstarch. Boil until thickened, 1 to 2 minutes. Transfer to a medium bowl and refrigerate until cool, about 20 minutes.

Step 2

Meanwhile, in a medium bowl, whip heavy cream to stiff peaks; set aside. In a large bowl, combine yogurt and remaining 2/3 cup sugar. Fold in whipped cream.

Step 3

Break ladyfingers in half. Place half of them in a 2-quart glass bowl or trifle dish. Drizzle cookies with 1 tablespoon liqueur, if using, and dollop with one-third of yogurt mixture. Spoon half of berries over yogurt mixture, then drizzle 3 to 4 tablespoons thickened juices. Layer another one-third of yogurt mixture over berries, followed by a layer of remaining ladyfingers. Drizzle with remaining 1 tablespoon liqueur and dollop with remaining yogurt mixture. Top with remaining berries and 3 to 4 more tablespoons thickened juice. Refrigerate until chilled, about 2 hours, before serving.