There are times, and I assume this happens to every home cook out there, when you just nail it. You get this idea for something to make, and you get to making it, and then it's made, and then you look at it this thing you made and you can't really believe that what you made came out precisely as you envisioned making it and you just say to yourself with a tone of rapturous and disbelieving wonder: "Man... I made the shit out of that."
These moments don't happen often. They're vanishingly rare, in fact. But when they do happen, and when they happen at a time when it's really important, there are few things better.
This cake was one of those moments. The approach of autumn is marked each year by Mrs. Culinarian's birthday, for which I try to make something special. She's very much a fan of chocolate (understandable) and hazelnuts (weirdo), and something of a cake fiend, so the chocolate-hazelnut mousse cake emerged as the obvious choice.
Any idiot can bake a chocolate cake and dump some hazelnutty mousse on there. This one had to be elegant. Classy. Sophisticated. And the sure-fire, can't-miss method for classing up any dessert is the CHOCOLATE LATTICE, a brittle, interlocking web of chocolate that sits demurely above your pastry, providing both textural variance and a pleasing visual aesthetic.
Chocolatiering is typically a tremendous pain and requires vast reservoirs of patience, but the lattice actually isn't that difficult, compared to other, less-forgiving chocolatiering pursuits. And it'll lend whatever you're making a look of professionalism even though you have little idea what you're doing. Fake it while you make it.
The cake portion of the cake is chocolatey and tangy, owing to some elevated buttermilk content. The mousse gets its hazelnut punch from a generous helping of Nutella. It's both light and rich, courtesy of whipped cream and marscapone. With the lattice on top, it's all class. It does require some careful, artful construction and a little more know-how than a simple layer cake, but it's a special occasion kind of thing so quit whinging and put in a little effort for the people you care about.
The cake recipe is courtesy of Bon Apetit (the cake in the photo BA uses on the recipe page is tremendously darker than the actual cake, for some reason) and the mousse comes from Epicurious. Make a half-recipe of the cake (use a springform pan, if you have one) and a full recipe of the mousse and follow the assembly instructions below.