The double part refers to the mousse and the meringues both being chocolate. Don’t be put off by the relative length of this recipe, it really is easy and can be made hours ahead and even be stored for a day or two before final assembly. Once put together though, it must be eaten quickly as the delicate mousse doesn’t take long to deflate, out of the refrigerator and the meringues will quickly turn soggy once in contact with the mousse. The main attraction apart from how pretty this is wo...