In a medium bowl, whip the heavy cream until soft peaks form. Gradually add the powdered sugar and vanilla extract, continuing to whip until stiff peaks form.

In another bowl, gently fold the mascarpone cheese into the whipped cream until well combined and smooth.

In a shallow dish, combine the cooled coffee and coffee liqueur, if using. Dip each ladyfinger into the coffee mixture for about 1-2 seconds, ensuring they are soaked but not soggy.

In a 9x9-inch dish, layer half of the soaked ladyfingers on the bottom. Spread half of the mascarpone mixture over the ladyfingers, then add 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.