Add the espresso to a large bowl. Dunk the ladyfingers into the espresso and then place on a rimmed baking sheet. Pour the remaining espresso over the ladyfingers and set aside to soak.
In the bowl of a stand mixer fitted with a whisk attachment, beat the egg whites on high speed until they form soft peaks. Add 1/2 cup of the sugar and continue to beat on high until stiff peaks form. Transfer the egg whites to another bowl and set aside.
Make a double boiler by fitting a large heatproof bowl over a simmering pot of water. Add the egg yolks, remaining 1 cup sugar and Marsala to the bowl. Whisk continually until the mixture is pale yellow and reaches the ribbon stage (it will be thick enough that when the whisk is lifted, the mixture will flow onto the surface and momentarily hold a ribbon pattern). Remove the bowl from the pot and let the mixture cool to room temperature.
In the bowl of a stand mixer fitted with a whisk attachment, whip the mascarpone until fluffy. Fold the mascarpone into the cooled egg yolk mixture. Then, gently fold the yolk-and-mascarpone mixture into the egg whites.
To assemble, in an individual serving glass, place a few spoonfuls of the tiramisu custard over the bottom. Break a soaked ladyfinger in half and place it on top of the custard. Add a few more spoonfuls of custard followed by another ladyfinger. Dust with shaved chocolate. Repeat with the remaining ingredients, making 8 servings. Refrigerate until ready to serve.