A chocolate challenge

I love an occasion to bake a cake. It gives me opportunity to try out a new recipe and to learn some new techniques. I was instantly drawn to this cake in Epicurious for its shiny, drippy, chocolaty ganache that runs over the side of a mousse cake.

I did o.k. until I got to the ganache. The shortbread on the bottom came out perfect, though I would double the recipe next time for greater texture contrast with the mousse. It think it would also give the cake a stronger hazelnut flavor. The mousse came out well, too, though I prefer a more dense mousse with some heft.

The ganache, which I thought would be a piece of cake (no pun intended, truly), turned out to be a disaster. It seems so easy with just two ingredients - chocolate and cream. But it's all about timing, temperature and technique. It came out grainy and lumpy the first two times, and on the third attempt it came out smooth but not liquid enough to run over the side. I never got a photo of the final cake with the sad-looking ganache, because I was in such a frenzy to finish up and catch a bus. It wasn't the prettiest thing, but the crowd seemed to like it enough.

I did a little research on ganache. The key to ganache making is to use excellent quality chocolate (for good fat content), bring the cream to a boil (not just a simmer, as the recipe indicated), and cut the chocolate into tiny pieces (smaller than 1/4" pieces) that can melt quickly. I also think this method or pouring the cream over the chocolate would work better than the other way around. And finally THE most important thing: when you pour the cream over the chocolate, allow it to sit for a few minutes before you do anything with it. Don't move it, stir it, swoosh it, or even lay a finger on it. Just leave it alone! This keeps the fat molecules from separating out and creating a lumpy grainy mass of nastiness.

Best of luck to you if you give this a try!

Recipe: Chocolate-Hazelnut Mousse Cake
Adapted from Epicurious
Ingredients
For shortbread base
2 tablespoons hazelnuts, toasted and skins rubbed off
3 tablespoons sugar
1/2 cup all-purpose flour
1/2 stick (1/4 cup) unsalted butter, softened
2 tablespoons unsweetened Dutch-process cocoa powder
1/8 teaspoon salt

For mousse
1 teaspoon unflavored gelatin (from a 1/4-oz envelope)
3 tablespoons cold water or Frangelico (a hazelnut liquer) for extra hazelnut flavor
1/2 cup chocolate hazelnut spread such as Nutella (5 oz) [Note: Trader Joe's and Whole foods have spreads that are cheaper and healthier respectively]
1/2 cup mascarpone (1/4 lb)
1 1/2 cups chilled heavy cream
2 tablespoons unsweetened Dutch-process cocoa powder
3 tablespoons sugar

For ganache
1/4 cup plus 1 tablespoon heavy cream
3 1/2 oz fine-quality bittersweet chocolate (not unsweetened), chopped

Special equipment: an 8-inch (20-cm) springform pan; parchment paper; food processor if you don't want to chop all the nuts and chocolate by (hand like I did).

Preparation
Make shortbread base:
Put oven rack in middle position and preheat oven to 350°F. Invert bottom of springform pan (to make it easier to slide shortbread base off bottom), then lock on side of pan and line bottom with a round of parchment paper.

If using a food processor, pulse hazelnuts with sugar in a food processor until nuts are finely chopped. Add flour, butter, cocoa, and salt and pulse just until a dough forms. If chopping by hand, chop hazelnuts fine, then combine flour, butter, cocoa and salt with a mixer just until a dough forms.

Press dough evenly onto bottom of springform pan with your fingers. Prick all over with a fork, then bake until just dry to the touch, about 18 to 20 minutes. Transfer base in pan to a rack to cool completely, about 30 minutes. Remove side of pan and carefully slide out parchment from under shortbread, then reattach side of pan around shortbread base.


Make mousse while shortbread cools:
Sprinkle gelatin over water or Frangelico in a 1- to 1 1/2-quart heavy saucepan and let stand until softened, about 5 minutes. Heat gelatin mixture over low heat, stirring, just until gelatin is melted, about 2 minutes. Whisk in chocolate hazelnut spread until combined and remove from heat.

Whisk together mascarpone and chocolate hazelnut mixture in a large bowl. Beat together cream, cocoa powder, and sugar in another large bowl with an electric mixer at low speed until just combined, then increase speed to high and beat until cream just holds soft peaks. Whisk one third of whipped cream into mascarpone mixture to lighten, then fold in remaining whipped cream until well combined. Spoon filling onto shortbread base in pan, gently smoothing top, then chill, covered, at least 3 hours.

Make ganache and glaze cake:
Bring cream to a simmer in a small heavy saucepan and remove from heat. Add chocolate and let stand 1 minute, then gently whisk until completely melted and smooth. Transfer ganache to a small bowl and cool, stirring occasionally, until slightly thickened but still pourable, about 20 minutes.

Run a warm thin knife around inside of springform pan, then remove side. Slide cake off bottom of pan and transfer to a serving plate. Pour ganache onto top of cake and spread, allowing excess ganache to drip down sides.

Cooks' notes:
• Cake, without glaze, can be chilled up to 2 days.
• Cake can be glazed 6 hours ahead and chilled, uncovered.