In a large bowl, whisk the egg yolks and sugar together until the mixture becomes pale and slightly thickened, about 2-3 minutes.

1. In a separate bowl, beat the mascarpone cheese until smooth and creamy.
2. In another bowl, whip the heavy cream with vanilla extract until stiff peaks form.
3. Gently fold the mascarpone cheese into the egg mixture until combined. Then, fold in the whipped cream, being careful not to deflate the cream.
4. Once the cream is well mixed, set it aside.
5. In a shallow dish, combine the cooled espresso or coffee with the rum or coffee liqueur (if using).
6. Quickly dip each ladyfinger into the coffee mixture. Do not soak them; just dip briefly so they are moistened but not soggy.
7. Arrange a layer of the dipped ladyfingers in the bottom of a 9×13-inch baking dish or a trifle dish.
8. Spread half of the mascarpone cream mixture over the ladyfingers, smoothing it out with a spatula.
9. Repeat the process with another layer of dipped ladyfingers and the remaining mascarpone cream mixture.
10. Cover and refrigerate the tiramisu for at least 4 hours, preferably overnight, to allow the flavors to meld together.
11. Just before serving, dust the top of the tiramisu with unsweetened cocoa powder using a fine mesh sieve.
12. Optionally, garnish with dark chocolate shavings for an extra touch of elegance.
13. Serve chilled and enjoy the creamy, coffee-infused delight!