I want to make a cake covered with fondant, because I love the smoothness of it and would like to have the top of the cake perfectly smooth. I was wondering if I could still do a basketweave on the sides with buttercream though? Will the bc break down the fondant in any way, or fall off of it? TIA!

how far in advanced are you making the cake? The buttercream will keep the fondant soft, but I don't think it will necesarily break it down; not right away, anway.

It's actually a sort-of last minute cake for a friend. I just found out her anniversary is today, and she wasn't pleased with her original wedding cake(which I did NOT make), so I am going to make her another one. So it's not really in advance, they will probably eat it shortly after I give it to them.