Make the Mascarpone Cream: In a medium bowl, use an electric mixer to beat the egg yolks and sugar on high speed until the mixture is thick, pale, and fluffy (about 5 minutes). Add the mascarpone cheese and mix until smooth. In a separate bowl, whip the cold heavy cream until stiff peaks form. Gently fold the whipped cream into the mascarpone mixture.

Prepare the Coffee Dip: In a shallow dish, combine the cooled coffee or espresso and the coffee liqueur (if using).

Assemble the Tiramisu: Quickly dip each ladyfinger into the coffee mixture, one at a time, making sure not to let it get too soggy. Arrange a single layer of the soaked ladyfingers in the bottom of a 9x9-inch baking dish.

Layer the Dessert: Spread half of the mascarpone cream mixture evenly over the ladyfinger layer. Dust with half of the cocoa powder. Repeat the process with a second layer of soaked ladyfingers, the remaining cream, and the rest of the cocoa powder.

Chill and Serve: Cover the dish with plastic wrap and refrigerate for at least 4 hours, or preferably overnight. The chilling time allows the ladyfingers to soften and the flavors to fully meld. Before serving, dust with a final layer of cocoa powder and garnish with chocolate shavings.