01 - Whisk egg yolks with powdered sugar in a heatproof bowl set over a pot of simmering water, creating a double boiler. Whisk continuously for 2-3 minutes until the mixture thickens and becomes pale in color. Remove from heat and let cool slightly.
02 - In a clean mixing bowl, beat the cold heavy cream using an electric mixer or whisk until stiff peaks form. Set aside.
03 - Gently fold the mascarpone cheese into the cooled egg yolk mixture until smooth and well combined. Then carefully fold in the whipped cream until fully incorporated, maintaining a light and airy texture.
04 - Combine the cooled coffee with coffee liqueur in a shallow dish wide enough to dip the ladyfingers.
05 - Quickly dip each ladyfinger into the coffee mixture for just 1-2 seconds per side. The biscuits should be moistened but not saturated or soggy. Work efficiently to prevent them from becoming too soft.
06 - Arrange half of the dipped ladyfingers in a single layer in an 8-inch square dish. Spread half of the mascarpone mixture evenly over the biscuits using a spatula.
07 - Repeat with another layer of dipped ladyfingers, followed by the remaining mascarpone mixture. Smooth the top surface with your spatula.
08 - Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours, preferably overnight. This allows the flavors to meld and the texture to set properly.
09 - Just before serving, dust the top generously with unsweetened cocoa powder using a fine-mesh sieve. Garnish with dark chocolate shavings if desired. Slice and serve chilled.