Probably the heavy dose of tonka bean. Check out F Feragamo Black pH, it's even creamier and louder than La Nuit, and lasts a lot longer. But has a stronger orange note in the opening, which makes it different than La Nuit.
Probably a singular or combination of aroma chemicals. MFK frags for example all have a smooth/fuzzy signature. Might be worth posting something on the DIY board if you're really curious. Chris Bartlett and the others will probably have more specific knowledge to pass on about this.