After reading several forums. I am concerned about my boxed cakes holding up to be covered with the marshmallow fondant. Please, please, please tell me that it will. I have already made cakes and my fondant for my daughters "surprise" party on Sat. It is a three tier cake. I want to make it a hit not a disaster. Please help!

Covering them with a layer of ganache will help. The ganache makes the cake a little sturdier to hold up to the fondant. Check the forum index for ganache under fondant.

All my cakes are box cake mix's and all my cakes are covered in fondant. You can make the cakes more dense by adding sc and pudding. I have done both and they all have been just fine.

i use boxes and MMF, with buttercream and no problem at all.

I have done just fine with box cake mixes as is and fondant. If you are not sure still, then this is what I do to make my cakes sturdier for when I need to sculpt, etc.

I use Duncan Hines:

Add 1 small box of instant pudding (use a flavor that compliments your cake)
Add 1 extra egg (4 total)
Make your oil 1/2 cup instead of 1/3 cup.

Bake as you normally would.

I only use boxed cakes and MMF and have never had any problems. Hope everything works out for you.

Same here. I use DH box mix and homemade MMF over buttercream. I've never had a problem. I just chill my cakes before putting on the fondant.

box mix here too, what ever is on sale, not picky. then frost with bc and cover with fondant. seems fine to me, but then i am not an expert either.

Thanks for all the info. I am so glad to hear that hopefully everything will be ok. What type of buttercream do you guys use? I usually use a crusting BC. Is this ok or do I need a new recipe?

I use mixes straight out of the box and my fondant cakes hold up fine. I don't use really thick fondant, though (I HATE the "play-doh" look of thick fondant!). Matter of fact, when I first started doing fondant, I honestly wondered what the big deal was about the cakes holding up because I never had ANY problems what so ever.

theres no need to add anything extra. I use box mixes for all my cakes and never had an issue.

I use fondant over box mixes all the time and no problems yet. I like using ganache under the fondant though I have used IMBC too, both are great, and I always put the cake in the fridge for twenty minutes or so to firm up before I put the fondant on, works great.