In a medium saucepan, whisk together the egg yolks and granulated sugar until well combined.

Add the milk to the saucepan and cook over medium heat, stirring constantly until the mixture thickens and coats the back of a spoon. This should take about 5-7 minutes.

Remove the saucepan from heat and let the mixture cool to room temperature.

In a large mixing bowl, whip the heavy cream until soft peaks form.

Gently fold the mascarpone cheese and vanilla extract into the whipped cream until smooth and well incorporated.

Once the egg mixture has cooled, fold it into the mascarpone mixture until fully blended.

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

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 9x9-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 or overnight for the best flavor and texture.

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