Prepare the Coffee Mixture:
In a shallow dish, combine the brewed coffee and coffee liqueur (if using). Set aside to cool completely.
Make the Mascarpone Cream:
In a medium bowl, whisk the egg yolks and granulated sugar until pale and creamy.
Add the mascarpone cheese and vanilla extract, then beat until smooth.
In a separate bowl, whip the heavy cream to stiff peaks. Gently fold the whipped cream into the mascarpone mixture until fully incorporated.
Prepare the Egg Whites:
In another bowl, beat the egg whites to stiff peaks. Gently fold the whipped egg whites into the mascarpone mixture for an extra light and airy texture.
Assemble the Tiramisu:
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 an 8x8-inch dish or similar-sized container.
Spread half of the mascarpone cream over the ladyfingers, smoothing it out evenly.
Add another layer of soaked ladyfingers on top, followed by the remaining mascarpone cream.
Chill the Tiramisu:
Cover the dish with plastic wrap and refrigerate for at least 4-6 hours, or overnight for best results.
Serve:
Before serving, dust the top of the tiramisu with unsweetened cocoa powder using a fine mesh sieve.
Garnish with chocolate shavings if desired. Slice and serve chilled.