This recipe comes from the chef Joshua Pinsky of Penny in Manhattan’s East Village, and its sister restaurant, Claud (home of his pistachio Bundt cake). More of an aerated chocolate custard than a traditional mousse, it starts with a warm egg-cream base that melts chocolate and butter. Everything is then blended until smooth. A small yet integral amount of olive oil helps give this mousse its gorgeous sheen, slightly fruity flavor and silky texture. While this mousse is fabulous without the candied hazelnuts, they add a bit of crunch and sweetness to offset the mousse’s rich bitterness. (If you choose to forgo making caramel, a simple topping of toasted nuts works great, too.) The mousse sets up a bit matte, but a quick stir will restore its sheen and loosen it a bit.