NYT Cooking: There is very little that needs to be said about a chocolate mousse cake. This one lives up to its name. It is gloriously intense. But the whisked egg whites ensure that it has a balancing lightness. A slice of it, with a smattering of fresh raspberries and a dollop of cream, or better still, sour cream, is the perfect finale. It may also invite a certain inelegant gluttony at the end. I have noticed that even those who claim not to go in for desserts come back for more.