01 - Whisk egg yolks with powdered sugar in a heatproof bowl set over a pot of simmering water. Cook for 2-3 minutes until the mixture thickens and becomes pale in color. Remove from heat and allow to cool slightly.
02 - In a chilled 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 mixture until smooth and well combined. Then carefully fold in the whipped cream until fully incorporated.
04 - Combine the cooled coffee and coffee liqueur in a shallow dish. Stir to blend.
05 - Quickly dip each ladyfinger into the coffee mixture for 1-2 seconds per side. The biscuits should be moistened but not soggy or falling apart.
06 - Arrange half of the dipped ladyfingers in a single layer in an 8-inch square dish. Spread half of the mascarpone filling evenly over the biscuits.
07 - Repeat with a second layer of dipped ladyfingers, followed by the remaining mascarpone mixture. Smooth the top with a spatula.
08 - Cover the dish tightly with plastic wrap and refrigerate for at least 4 hours. Overnight chilling produces the best texture and flavor.
09 - Just before serving, dust the top generously with unsweetened cocoa powder. Add dark chocolate shavings as an optional garnish. Slice and serve cold.