In a shallow dish, combine the cooled 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 to the egg yolk mixture and gently fold until smooth and well combined.

In a separate 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 another bowl, beat the egg whites until stiff peaks form. Gently fold the egg whites into the mascarpone mixture until no white streaks remain.

Quickly dip each ladyfinger into the coffee mixture, making sure not to soak them, and layer them in the bottom of a 9x13 inch dish.

Spread half of the mascarpone mixture over the ladyfingers, smoothing it out evenly.

Repeat the process with another layer of dipped ladyfingers followed by the remaining mascarpone mixture.

Cover the dish with plastic wrap and refrigerate for at least 4 hours, preferably overnight.

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