In a mixing bowl, combine mascarpone cheese, heavy cream, powdered sugar, and vanilla extract. Whip until the mixture is smooth and forms soft peaks.
Prepare the coffee in a separate bowl and allow it to cool. Once cooled, dip each ladyfinger into the coffee for a couple of seconds, ensuring they are soaked but not soggy.
In a rectangular or square dish, lay a layer of soaked ladyfingers at the bottom. Spread half of the mascarpone mixture over the ladyfingers.
Add a layer of fresh berries over the mascarpone mixture, spreading them evenly.
Repeat the layers with the remaining ladyfingers, mascarpone mixture, and berries.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, preferably overnight, to allow the flavors to meld.
Before serving, dust the top of the tiramisu with cocoa powder for a touch of elegance.