Melt chocolate in top of double boiler.
Beat egg yolks until thick and lemony.
Add sugar, water, Cointreau and egg yolks to chocolate.
Cook slowly, stirring constantly, until thickened and smooth.
Cool.
Beat egg whites until stiff peaks form; fold into chocolate mixture.
Line sides and bottom of me- dium springform pan with split ladyfingers, placing flat side against pan.
Moisten ladyfingers with sherry.
Pour in half the chocolate filling; sprinkle with sliv- ered almonds.
Add another layer of ladyfingers, flat side down; moisten with sherry.
Add remaining chocolate filling; sprinkle with slivered almonds.
Cover with ladyfingers, flat side down; moisten with sherry.
Refrigerate for at least 12 hours.
Remove springform, leaving cake on bottom of pan.
Cover top of cake with whipped cream; garnish with mara- schino cherries or slivered almonds.
Ladyfingers should not be soggy.
Whipped cream may be sweet- ened and flavored with vanilla.