In a large mixing bowl, beat the mascarpone cheese with ½ cup (120 ml) of the Baileys Irish cream until smooth, light, and fully blended. Set aside.
16 oz (454 g) mascarpone cheese, ¾ cup (180 ml) Baileys Irish Cream
Set up a double boiler by placing a heat-safe mixing bowl over a medium pot of gently simmering water, making sure the water does not touch the bottom of the bowl. Add the egg yolks and granulated sugar and whisk constantly for 5 to 7 minutes, until the sugar has fully dissolved, the mixture has thickened slightly, and the color has lightened. Remove from heat.
6 large egg , ¾ cup granulated sugar
Gradually whisk the warm egg yolk mixture into the mascarpone mixture until fully incorporated and smooth.
In a separate mixer bowl, whip the heavy cream with the vanilla extract until medium peaks form. The cream should hold its shape with a slight bend at the tip.
16 oz (480 ml) heavy whipping cream, 2 tsps (10 ml) vanilla extract
Gently fold the whipped cream into the mascarpone mixture in two additions, taking care not to deflate the mixture. Set aside.
In a shallow bowl, combine the cooled espresso with the remaining ¼ cup (60 ml) Baileys Irish cream. If espresso is unavailable, extra-strong brewed coffee may be used.
1 cup (240 ml) espresso
Dip each ladyfinger briefly into the espresso mixture, allowing excess liquid to drip off. Arrange the dipped ladyfingers in a single, even layer in a 9×13-inch (23×33 cm) casserole dish.
40 ladyfingers cookies
Spread half of the mascarpone mixture evenly over the ladyfingers.
Repeat with a second layer of briefly dipped ladyfingers, followed by the remaining mascarpone mixture. Smooth the top into an even layer.
Using a fine mesh sieve or sifter, dust the top evenly with cocoa powder. You can also wait to add the cocoa powder until right before serving, your choice.
2 tbsps (10 g) unsweetened cocoa powder
Cover tightly and refrigerate overnight before serving.