This may sound funny but I made this cake last summer (June). I haven't been able to post it because I was so upset when it happened. Yes I cried. Fortunately or unfortunately it was for my own Alice in Wonderland themed wedding shower. The hat took me several hours that day and collapsed about 9pm that night. So we bought a store bought cake to go with the teapot. All very sad but I learned a lot and know exactly what I did wrong. I used a sleeve filling and torted the layers, 2 things I would never do today in an angled cake like this. It was buttercream and didn't fit in my fridge, another thing I wouldn't do. I think the weight of the top and the soft filling was just too much for the cake. I have vowed to remake this cake some day
I'm so sorry about your cake - it looked great. I made a mad hatter cake recently and didn't have any problems. I think this was because:
1. I used a firm chocolate cake
2. I filled it with thin layers of chocolate ganache
3. I used chocolate ganache as the coating beneath the fondant.
If you use a ganache made with 2 parts chocolate to 1 part cream, it sets firm at room temperature and effectively creates a shell around the cake. It still cuts and eats fine, but is firm enough to give the cake support.
But it sounds like you've figured out what went wrong. I'm sure you'll have success next time.
Thank you princess Cris. Yes I plan to use ganache and fondant next time. Buttercream and sleeve filling was a flat out bad idea but I hadn't discovered the ganache thread at that point. I still cringe when I think about it but I'm happy it was for me and not for someone else's event. I'm a hobbyist and only do cakes for friends and family but it would have been a bigger disaster if it was for someone else. Thanks for the support