Pour the espresso and Calvados into a shallow bowl and set aside. In a medium bowl, whisk together the egg yolks and the ¼ cup sugar until a slowly dissolving ribbon forms on the surface when the whisk is lifted. Whisk in the vanilla and mascarpone until satin smooth; set aside.
In a stand mixer with the whisk attachment, beat the egg whites with a pinch of salt until stiff peaks form. Add the 1 teaspoon sugar and whisk for about 1 minute more, or until the egg whites are glossy. Fold the mascarpone mixture into the egg whites and set aside.
Dip each ladyfinger in the espresso mixture, being careful to evenly coat both sides. Gently place the ladyfingers in the bottom of an 8-inch square baking dish. Cover the ladyfingers with the mascarpone mixture and smooth the top. Sprinkle with the grated chocolate. Cover and refrigerate for at least 2 hours or overnight. To serve, spoon the tiramisü into shallow bowls.