Perfecting a chocolate mousse seemed to take us forever. I was looking for a mousse that was rich, yet very definitely light, with a certain density about it. Also, I wanted to serve it freeform on a plate, but to do that, the flavor had to be elegant, even smoky. This is what we finally came up with, thanks largely to the work of Sophie Cookes, who was with us in the kitchen at the time. It needs to be served with something to counterbalance its intensity. Here I’ve chosen my favorite accompaniment: salty, almost burned, caramel. And cream, of course.

Steps

1. Make the mousse: Melt the chocolate slowly in a heatproof bowl set over a pan of gently simmering water, then remove from the heat and let cool slightly. Meanwhile, beat the egg yolks and half the sugar together in a bowl until pale and thick. Slowly incorporate the melted chocolate.
2. In a clean bowl, whisk the egg whites with the salt until soft peaks form, then gradually whisk in the remaining sugar. Carefully fold the egg whites into the chocolate mixture, a third at a time, until evenly combined. Pour into a large bowl, cover, and place in the refrigerator to set.
3. Make the sauce: Place the sugar and ½ cup water in a small heavy pan over very low heat and, without stirring, let the sugar dissolve. Once dissolved, turn up the heat to fairly high and bring to a boil. Cook until the caramel begins to color; this will take at least 5 minutes. When it starts to brown around the sides, watch it carefully, as it will then darken quite quickly.
4. Once the caramel has reached a deep mahogany color, quickly and carefully pour in the remaining 1¼ cups water. Cook, stirring, for another 2 minutes to loosen the caramel and ensure that it doesn’t set hard. Finally, throw in the salt, stir once or twice, then remove from the heat. Pour into a heatproof bowl and let cool, then chill.
5. Serve the dessert: Spoon the chocolate mousse onto plates and serve with the salty caramel and whipped cream, if using.