This luscious chocolate-hazelnut cake is coated with a ganache made from chocolate and cream. It's topped with a mountain of bittersweet chocolate curls, and surrounded by crunchy praline hazelnuts coated in tempered chocolate and rolled in cocoa powder.
Toast and peel the nuts for the cake and garnish at the same time. Bake the cake up to three days ahead; wrap well and keep at room temperature. The candied hazelnuts and chocolate curls can also be made three days ahead; store in airtight containers.