In a medium bowl, combine the heavy cream, mascarpone cheese, powdered sugar, and vanilla extract. Using an electric mixer, whip the mixture until soft peaks form.

In a shallow dish, mix the cooled coffee with the coffee liqueur, if using.

Quickly dip each ladyfinger into the coffee mixture, ensuring they are soaked but not soggy.

In a 9x9 inch baking dish, arrange a layer of dipped ladyfingers at the bottom.

Spread half of the mascarpone mixture over the ladyfingers, then layer half of the mixed berries on top.

Repeat the layers with the remaining ladyfingers, mascarpone mixture, and berries.

Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight for best results.

Before serving, dust the top with cocoa powder and garnish with additional berries if desired.