I apologise in advance as I'm sure this topic has been covered just recently, however, I've conducted a search and it comes up with nothing close to an answer
So.. I have my first request for a wedding topsy turvy cake.. and yes, I will practice before I work on the wedding cake I have no idea what to quote the client as I'm unsure of what pan sizes to use due to all the sculpting it requires. It will be to feed 100.. suggestions please!!
I calculate the servings same as a regular cake, based on the larger of the two measurements and I bake it a little taller. Most of the cake is just redistributed, there's only a little lost with the bottom half being 7". For instance, an "8x4" TT layer is an 8" cake on the top and a 7" cake on the bottom. i would usually bake 3" of cake to go with 1" of mousse filling, but in this instance I bake 4" of cake so with the filling it's more like 5" tall.
I just did a Topsy turvy cake in March. I had the hardest time trying to figure out how much cake I needed to serve 40. I seen this link for 100 servings. I hope this helps, it may not.