So a friend REALLY wants a 3D cake for her son’s bday.  It’s a Mario Brothers theme, so she wants a mushroom.  She also wants 5 chocolate cupcakes.  So I was thinking: make one recipe All Occasion Yellow Downy and one recipe of the chocolate version.  The yellow in 9” rounds to cut down to 6” (I don’t want to buy new pans just for this) and stack for the mushroom stem.  Put most of the chocolate batter in an oven-safe bowl for the mushroom top, then a half dozen cupcakes with the leftovers.  Possibly put a straw in the stem.  Put mushroom top on cake board cut to size and put it on the stem once I get to the party. She wants it all fondant…which I’ve actually never really done…I know, I’m crazy!  I was thinking chocolate neoclassic buttercream with marshmallow fondant (a friend said this was super easy).  Here are my questions:

1.  Is this a totally crazy idea?  Any suggestions?
2.  I just read a senior member saying she uses the crisco/spackle type frosting for under her fondant because it sticks better.  Is Rose’s buttercream not going to work with this cake?
3.  Do you think I’ll need two batches of buttercream?  fondant?
4.  Will a stainless steel mixing bowl work?
5.  Will this cake recipe not be firm enough for this type of thing? 
6.  Should I consider Rose’s frosting for in between layers and the cupcakes and the crisco frosting for the outer parts for the fondant?? 

Thanks in advance!!  : )

Also…will two rounds look tall enough for a stem?

I have never tried this sort of thing…and there are other’s on this blog that may have more information…but I can say that the cakes are very very tender, and don’t bake well in pans that are more than 2 1/2” tall. There is a website called Cakecentral.com where this sort of thing is discussed in more depth than it is on this forum. Hope this is helpful

Thank you very much for the information!  After researching some more, I decided against doing it for her, which she is completely okay with.  It’s just beyond me right now.  : )