In a large bowl, whip the heavy cream until stiff peaks form. In a separate bowl, beat the mascarpone cheese, powdered sugar, and vanilla extract until smooth. Gently fold the whipped cream into the mascarpone mixture until fully combined.

In a small bowl, mash half of the blueberries with 1 tablespoon sugar. Set the rest of the blueberries aside for garnish.

In a shallow dish, combine the cooled coffee and blueberry preserves. Quickly dip the ladyfingers into the coffee mixture, making sure not to soak them. Arrange a layer of dipped ladyfingers in the bottom of a 9x9-inch dish or trifle bowl.

Spread half of the mascarpone mixture over the ladyfingers. Spoon half of the mashed blueberries over the mascarpone layer, then add another layer of dipped ladyfingers.

Spread the remaining mascarpone mixture on top, smoothing it into an even layer. Finish by decorating with a light dusting of cocoa powder. Top with the remaining fresh blueberries and/or additional whipped topping, if desired..

Refrigerate for at least 4 hours, or overnight, to allow the flavors to meld. Serve chilled.