1. Prepare the Cream Layer: In a heatproof bowl set over simmering water, whisk the egg yolks and sugar until the mixture becomes thick and pale. Remove from heat and gently fold in the mascarpone cheese until smooth. In a separate bowl, whip the heavy cream until stiff peaks form, then fold it into the mascarpone mixture.

2. Prepare the Coffee Mixture: In a shallow dish, combine the cooled espresso or coffee, sugar, and vanilla extract.

3. Assemble the Tiramisu: Quickly dip each ladyfinger into the coffee mixture, then arrange them in a serving dish. Spread half of the creamy mascarpone mixture over the ladyfingers, then repeat the process with another layer of dipped ladyfingers and the remaining cream.

4. Chill the Tiramisu: Cover and refrigerate the assembled tiramisu for at least 4 hours, or preferably overnight, to allow the flavors to meld and the dessert to set.

5. Serve and Enjoy: Before serving, dust the top of the tiramisu with the unsweetened cocoa powder. For an extra touch of elegance, garnish with dark chocolate shavings.