Preparation Steps

• In a heatproof bowl set over a pot of simmering water (make sure the bowl doesn't touch the water), whisk together the egg yolks and granulated sugar until pale and thick. This is a double boiler method and cooks the yolks.
• Remove the bowl from the heat and continue whisking until the mixture cools completely. It should be thick and ribbon-like.
• In a separate bowl, whip the cold heavy cream until stiff peaks form. Be careful not to over-whip.
• Gently fold the softened mascarpone cheese into the cooled egg yolk mixture until just combined and smooth.
• Fold the whipped cream into the mascarpone mixture until no streaks remain.
• In a shallow dish, combine the cooled coffee and coffee liqueur (if using).
• Quickly dip each ladyfinger into the coffee mixture, ensuring they are moistened but not soggy. Place a layer of dipped ladyfingers in the bottom of a serving dish (approximately 8x8 inch).
• Spread half of the mascarpone cream mixture evenly over the ladyfingers.
• Repeat the layering process with another layer of dipped ladyfingers and the remaining mascarpone cream mixture.
• Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours, or preferably overnight, to allow the flavors to meld and the tiramisu to set.
• Just before serving, dust the top generously with unsweetened cocoa powder using a fine-mesh sieve.