Melt some bittersweet chocolate with espresso and beat eggs with sugar over a double boiler.
Beat the egg mixture and chocolate mixture; bring some egg whites to soft peaks, add sugar and bring to stiff peaks: fold into chocolate mixture. This fabulous mousse — from Julia Child's Mastering the Art of French Cooking — will form the second layer of the following cake:
One layer of chocolate chiffon (with a splash of kirsch), a layer of Julia's mousse (with kirsch in lieu of orange liqueur), another layer of chiffon, a layer of sour cherries (stewed, set with tapioca starch and finished with—you guessed it—kirsch), more chiffon. I finished this with a crumb coat (it sets the top) of mousse followed by a generous glaze of chcocolate ganache.
Serve with boozy (read: kirsch-laden) whipped cream. Add candles (and sour cherries soaked in Everclear, orange and hibiscus) and it's the cake for a fabulous friend's birthday!