Prepare the Cream Mixture:
In a mixing bowl, whisk the egg yolks and sugar together until pale and thick.
Place the bowl over a pot of simmering water (double boiler) and whisk continuously for 5–7 minutes until the mixture thickens slightly. Remove from heat and let cool.
Fold the mascarpone cheese into the cooled egg yolk mixture until smooth.
Whip the Cream:
In a separate bowl, beat the heavy cream until stiff peaks form.
Gently fold the whipped cream into the mascarpone mixture, ensuring it remains light and airy.
Prepare the Coffee Dip:
In a shallow dish, mix the cooled coffee and coffee liqueur (if using).
Assemble the Tiramisu:
Quickly dip each ladyfinger into the coffee mixture (do not soak). Arrange a layer of soaked ladyfingers in the bottom of your baking dish.
Spread half of the mascarpone cream mixture evenly over the ladyfingers.
Add another layer of coffee-dipped ladyfingers on top, followed by the remaining mascarpone cream.
Chill:
Cover the dish and refrigerate for at least 6 hours, preferably overnight, to allow the flavors to meld.
Garnish and Serve:
Just before serving, dust the top generously with cocoa powder using a sifter. Add chocolate shavings if desired.