Whip the Cream to Stiff Peaks: Pour the cold heavy cream into a large mixing bowl. Using an electric mixer on medium speed, begin whipping the cream. Gradually add the granulated sugar and vanilla extract as you whip. Continue until firm peaks form—when the cream holds a stiff peak without falling.
Combine Mascarpone Cheese: Transfer the softened mascarpone cheese to a separate bowl. Gently fold in the whipped cream until fully combined and smooth, creating a light, fluffy mascarpone cream mixture. Be careful not to overmix to maintain the airy texture.
Prepare the Coffee Soak: In a shallow bowl, mix the chilled espresso with the coffee liqueur if using. This mixture will flavor and moisten the ladyfingers.
Dip and Layer Ladyfingers: Quickly dip each ladyfinger into the coffee mixture—just enough to moisten without soaking—about one second per side. Arrange a single layer of dipped ladyfingers evenly in the bottom of an 8x8-inch baking dish.
Spread the First Mascarpone Layer: Spoon half of the mascarpone cream over the ladyfinger layer. Use a spatula to gently smooth it out into an even layer.
Repeat Ladyfinger Layer: Dip the remaining ladyfingers briefly in the coffee mixture and layer them evenly on top of the mascarpone cream.
Finish with Mascarpone Cream: Top with the remaining mascarpone mixture, spreading it smoothly to cover the ladyfingers completely.
Chill and Dust: Cover the dish with plastic wrap and refrigerate for at least 3-4 hours, or overnight for the best flavor melding. Just before serving, dust the top generously with cocoa powder using a fine mesh sieve for an even, delicate finish.