In a large mixing bowl, beat the egg yolks and granulated sugar together until the mixture is pale and fluffy (about 5 minutes).
Add the mascarpone cheese and vanilla extract to the egg yolk mixture. Mix until smooth and well combined.
In a separate bowl, whip the heavy cream until stiff peaks form. Gently fold this whipped cream into the mascarpone mixture until fully incorporated.
In another bowl, whisk the egg whites until soft peaks form. Carefully fold the egg whites into the mascarpone cream mixture, being mindful not to deflate the mixture.
Quickly dip each ladyfinger into the cooled coffee, making sure not to soak them too long (just a second on each side).
In a 9x9-inch baking dish, layer half of the soaked ladyfingers on the bottom.
Spread half of the mascarpone mixture over the ladyfingers, smoothing it out evenly.
Repeat the process with another layer of soaked ladyfingers and the remaining mascarpone mixture.
Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight to allow the flavors to meld.
Before serving, dust the top generously with unsweetened cocoa powder and garnish with dark chocolate shavings.