Here is a step-by-step method to make classic tiramisu:

1. Prepare the espresso mixture by combining brewed espresso and optionally some dark rum or coffee liqueur in a medium bowl.
2. Make the mascarpone cream mixture:
   • Beat mascarpone cheese with some rum (optional) until smooth.
   • Separately, whisk egg yolks and sugar over simmering water (double boiler) until thick and pale yellow (about 5-8 minutes).
   • Mix the egg yolk custard into the mascarpone until combined.
   • Whip heavy cream with vanilla extract until stiff peaks form, then fold gently into the mascarpone mixture.
3. Quickly dip ladyfinger cookies into the espresso mixture – do not soak too long to prevent sogginess.
4. Arrange a layer of the dipped ladyfingers in a dish.
5. Spread half of the mascarpone cream mixture evenly over the ladyfingers.
6. Repeat with another layer of dipped ladyfingers and then the remaining mascarpone cream.
7. Dust the top generously with unsweetened cocoa powder.
8. Refrigerate for at least 2-4 hours, ideally overnight, to allow flavors to meld and the tiramisu to set well.

This process creates a creamy, coffee-flavored layered dessert with a rich mascarpone custard and delicate ladyfingers soaked in espresso and rum or coffee liqueur. The chilling step is important for the best texture and flavor. Variations exist, including versions without raw eggs by using whipped cream in place of egg whites or gently cooking the egg custard (zabaglione method). But the above is a classic method with the traditional mascarpone custard and coffee-soaked ladyfingers.