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

In a large mixing bowl, whisk the egg yolks and granulated sugar together until the mixture is pale and creamy, about 5 minutes.

Add the mascarpone cheese to the egg yolk mixture and gently fold until smooth and well combined.

In another bowl, whip the heavy cream and vanilla extract until stiff peaks form. Carefully fold the whipped cream into the mascarpone mixture until fully incorporated.

In a separate bowl, beat the egg whites until stiff peaks form. Gently fold the beaten egg whites into the mascarpone mixture, being careful not to deflate the mixture.

Quickly dip each ladyfinger into the coffee mixture, ensuring they are soaked but not soggy. Arrange a layer of soaked ladyfingers in the bottom of a 9x13 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.