Prepare the Cream Mixture: In a saucepan, whisk together 6 egg yolks and 3/4 cup granulated sugar until smooth. Cook over medium heat, stirring continuously, until the mixture thickens—this usually takes about 5-7 minutes. Remove from heat and let it cool for a few minutes.
Whip the Heavy Cream: In a separate bowl, whip 1 1/4 cups of heavy cream to stiff peaks. Gently fold in 1 cup of mascarpone cheese until fully combined.
Combine Mixtures: Once the egg mixture has cooled, combine it with the mascarpone mixture. Stir until you achieve a smooth consistency.
Prepare Coffee Mixture: In a shallow dish, combine 1 cup of cooled strong brewed coffee and the optional 1/4 cup of coffee liqueur.
Assemble the Layers: Dip ladyfinger cookies in the coffee mixture one at a time, ensuring they’re soaked but not soggy. Layer them in your desired serving dish. Spread half of the mascarpone mixture over the ladyfingers.
Repeat Layers: Repeat the process with another layer of dipped ladyfingers followed by the remaining mascarpone mixture.
Chill: Cover and refrigerate the Tiramisu for at least 4 hours, or overnight for best results.
Serve: Before serving, dust the top with cocoa powder and garnish with dark chocolate shavings, if desired.