I quoted an 11x15 sheet cake enough to feed 40 people
Now would that mean I'd take one cake and torte and fill it, or am I making 2 cakes and layering them on top of one another and filling it??
It is for a kids b-day party and I want to make enough, but with 2 cakes layered is this far too much?
I don't know why, but sheet cakes are a mystery to me. 
An 11x15 2" tall is 35 2x2 servings (cut 5 on one side, 7 on the other). If you double the layers you will have 70 servings, which is way too much!! 
A 9x13 is 24 servings (2" tall) so if you made that a double layer that would be 48 servings. That's what I'd go with if it were me.
Just what kelleym said.
Here's a link to all four Wilton cake preparation and serving guides:
http://www.wilton.com/cake/cakeprep/baking/times/index.cfm
These guides tell you how much batter is required by pan size, at what temp. to bake and for how long.
The charts also give you servings per layer cake by pan size; either by wedding (1x2x4) or party (1-1/2x2x4) size serving.
For Sheet Cakes (look under party cakes). You can use party or wedding size slices or make single layers.
For single layer servings of 2x2x2 or 2x3x2 slices, see indydebi's posts:
http://forum.cakecentral.com/cake-decorating-ftopict-302303-.html
HTH
JanH, thanks for that - just to be sure, when Wilton says 2 layer, they mean 2 cakes stacked, not one cake torted??
Quote by @%username% on %date%
%body%