Pour your cold heavy whipping cream into a large, chilled mixing bowl. Beat on medium speed, gradually sprinkling in the granulated sugar and pouring in the vanilla extract. Whip until you achieve firm, stiff peaks. Do not over-mix.
Add the room-temperature mascarpone directly to your whipped cream bowl. Gently fold the soft cheese into the whipped cream using a large rubber spatula until beautifully smooth and fully combined. Set aside.
Pour your cold, prepared espresso and coffee syrup (if using) into a shallow, wide bowl for easy dipping.
Working quickly, take one ladyfinger cookie and rapidly dip it into the cold espresso mixture. Quickly flip it to coat the other side, then remove immediately (a rapid one-second dip is all you need).
Place the moistened cookie into an 8x8-inch glass baking dish. Repeat with more ladyfingers, arranging them closely together in a single, even layer to cover the bottom of the pan completely.
Scoop exactly half of the mascarpone mixture out and spread it directly over your arranged ladyfingers. Use a small offset spatula to smooth it evenly to the edges.
Repeat the quick dipping process with the remaining ladyfingers, arranging them neatly on top of the first cream layer.
Scoop the remaining mascarpone mixture onto the second cookie layer and smooth it out meticulously until the top surface is flat and pristine.
Fill a fine-mesh sieve with unsweetened cocoa powder and generously dust the entire surface with a thick, even layer.
Cover the baking dish tightly with plastic wrap and chill in the refrigerator for at least 3 hours (overnight is highly recommended) before slicing and serving.