Butter sides and bottom of 8-inch springform pan. Sprinkle with confectioners' sugar; swirl pan to coat evenly. Separate ladyfingers. Line sides of springform pan with ladyfingers, rounded sides against pan.
Crumble remaining ladyfingers; press into bottom of pan. Combine over hot
(not boiling) water, Nestle Toll House semi-sweet chocolate morsels and water. Stir until morsels are melted and mixture is smooth. Transfer to large bowl. Add egg yolks, 1 at a time, beating well after each addition.
Set aside. In 1-1/2 quart bowl, beat egg whites until soft peaks form.
Gradually add sugar; beat until stiff peaks form. Fold egg whites and whipped cream into chocolate mixture. Pour into ladyfinger-lined pan.