In a shallow dish, combine the cooled brewed coffee and coffee liqueur, if using. Set aside.

In a mixing bowl, whisk the egg yolks and granulated sugar together until the mixture is pale and creamy. Add the mascarpone cheese and vanilla extract, mixing until smooth and well combined.

In a separate bowl, beat the heavy cream until stiff peaks form. Gently fold the whipped cream into the mascarpone mixture until fully incorporated.

In another bowl, whisk the egg whites until stiff peaks form. Carefully fold the egg whites into the mascarpone mixture, being cautious not to deflate the mixture.

Quickly dip each ladyfinger into the coffee mixture, ensuring they are soaked but not soggy. Lay half of the soaked ladyfingers in a single layer in the bottom of a 9x9-inch dish.

Spread half of the mascarpone mixture over the layer of ladyfingers. Repeat with another layer of soaked ladyfingers and the remaining mascarpone mixture.

Cover the dish with plastic wrap and refrigerate for at least 4 hours, preferably overnight, to allow the flavors to meld and the dessert to set.

Before serving, dust the top with cocoa powder and garnish with dark chocolate shavings, if desired.