Pour the espresso into a small shallow bowl and the Kahlüa into a separate small bowl. Have ready six 1/2-cup ramekins.

With an electric mixer on medium-high speed, beat the egg yolks with 4 tablespoons of the sugar in a large bowl, until the mixture is thick and pale yellow, 4 to 5 minutes. Reduce the speed to low and beat in the mascarpone and vanilla until they are well combined.

With the electric mixer on high speed and clean beaters, beat the egg whites with the remaining 1 tablespoon of sugar in a medium bowl until soft peaks form, about 1 minute. Lightly fold the egg whites into the mascarpone mixture.

Split the ladyfingers lengthwise, and cut them to fit the ramekins. Dip the sliced ladyfingers, 1 at a time, into the espresso. Line the bottom of the ramekins with enough ladyfingers to make a single layer. Drizzle 1 teaspoon of the Kahlüa over the ladyfingers in each ramekin, then cover them with 1/4 cup of the mascarpone mixture. Repeat, making another ladyfinger and mascarpone layer in each ramekin. Sprinkle 1/2 teaspoon of the shaved chocolate on top of each tiramisu.

Cover the ramekins with plastic wrap and refrigerate them at least 2 hours or up to 4 hours. Serve cold.