I recently made a cake with a superb french BC recipe. I have a cake coming up to do that i need to use MMF for for decoration purposes but would love to use the FBC recipe again. My only fear is do you think FBC would cause the MMF to slide since it doesnt really crust? If so, does anyone have a great chocolate icing recipe i can use with MMF?
Whether or not the icing crusts is not an issue for applying fondant. The only real issue is high water content, which is generally only a problem if you are icing the cake with whipped cream or Bettercreme (i.e.: you can't fondant a whipped cream cake). So you're fine!
Many people here cover MBC (meringue bc) cakes w/fondant all of the time. My understanding is that a FBC is similar, only it uses yolk instead of egg whites. The important thing is to be sure to refrigerate your cake til the icing is firm, before attempting to apply the fondant.
If you end up switching recipes for some reason, really any chocolate icing is fine. IMBC with chocolate added (yum!), traditional powdered sugar BC (Toba Garrett's is a good choice), whipped ganache, fudge icing/"blender ganache" are a few that come to mind . Personally, I vote for the FBC, if you already love it then you should use it!