Approximately 14 ounces packaged Savoiardi ladyfingers (36 cookies)
Approximately 1 cup strong coffee, preferably Italian espresso, cooled
Cocoa, for garnish
Whip sugar and egg yolks until pale gold and slightly fluffy, then beat in mascarpone until well-combined.
In a separate bowl, with clean beaters, beat egg whites until stiff. Gently fold them into the mascarpone mixture.
One by one, dip the ladyfingers into the coffee and cover the bottom of a glass or ceramic 13- by 9-inch pan with half of them. Cover the layer of ladyfingers with about half the mascarpone mixture, then the remaining coffee-dipped ladyfingers, then the remaining mascarpone.
Cover tightly and refrigerate for 4 to 6 hours, and preferably overnight.
Before serving, sift a few teaspoons of unsweetened cocoa over the top.