It’s all about the chocolate, isn’t it? Use second-rate chocolate, get second-rate mousse. My pastry chef always insists—and I mean insists—on expensive Valrhona chocolate (see Suppliers). And as she knows a helluva lot more about pastry than I do, I figure I’d better agree.
In the medium pot, bring a few cups of water to a simmer. Place a mixing bowl over the pot and add the chocolate. Stir gently to help the chocolate melt and prevent it from scorching. Whisk in the Grand Marnier, then whisk in the butter,