Please tell me I didn't make a fatal error here. I just crumb coated a chocolate cake in chocolate SMBC and then realized that my design called for a white fondant covering. This may be a stupid question but will the chocolate show through? I'm new to this so I didn't even think about it until now.

I'm just picturing what happens when I rock a leopard print bra under a white t-shirt.

i think as long as you go a little thicker on the fondant it will be ok. it might not be "white" but it will be as close as you can get. it helps that the whole cake is one color so it wont be as noticable

A lot of decorators use chocolate ganache under their white fondant cakes. I have use chocolate icing under white fondant, and it did not show.