Classic Tiramisù

5 large egg whites
Salt
4 large egg yolks
1/3 cup sugar
Two 8 3/4-ounce containers mascarpone, at room temperature
1/2 cup strong brewed espresso, cooled
About 17 ladyfingers (from a 17-ounce package)
Unsweetened cocoa powder, for dusting
1/2 cup semisweet or bittersweet chocolate curls, made with a vegetable peeler

In a medium bowl, using a handheld electric mixer, beat the egg whites with a pinch of salt at high speed until firm peaks form. In another medium bowl, beat the egg yolks with the sugar until pale and thickened. At low speed, beat the mascarpone into the yolks. Fold the beaten whites into the mascarpone mixture.

Spread half of the mascarpone mixture in a 9-by-13-inch glass baking dish. Pour the espresso into a shallow bowl. Dip the ladyfingers in the espresso until evenly moistened and arrange in a layer on the mascarpone mixture; you may need to break a few in half to make them fit. Spread the remaining mascarpone mixture on top. Sift cocoa powder over the tiramisù. Cover and refrigerate overnight.

Scatter the chocolate curls evenly over the tiramisù and serve.

MAKE AHEAD: The tiramisù can be refrigerated for up to 2 days.