Creating Tiramisu is a straightforward process if you follow these simple steps:

1. Prepare the Custard: In a medium saucepan, whisk together the egg yolks and granulated sugar. Cook over medium heat, stirring constantly, until the mixture thickens (about 10 minutes). Remove from heat and stir in the milk. Let cool.
2. Whip the Cream: In a large bowl, whip the heavy cream until stiff peaks form. Gently fold in the mascarpone cheese until smooth and fully combined.
3. Combine Mixtures: Once the egg yolk mixture has cooled, fold it into the mascarpone and cream mixture. Be careful to maintain the airy texture.
4. Prepare the Coffee Mixture: In a shallow dish, combine the brewed coffee and coffee liqueur, if using.
5. Soak the Ladyfingers: Quickly dip each ladyfinger into the coffee mixture, ensuring they are soaked but not soggy.
6. Layer the Dessert: In a 9×13 inch dish, arrange a layer of soaked ladyfingers at the bottom. Spread half of the mascarpone mixture over the ladyfingers. Repeat with another layer of soaked ladyfingers and the remaining mascarpone mixture.
7. Chill: Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight for the best flavor and texture.
8. Dust with Cocoa: Before serving, dust the top with unsweetened cocoa powder and garnish with dark chocolate shavings if desired.

Following these steps will lead you to a delightful Tiramisu that is sure to impress!