Chocolate Cake In A 12X12X3 Pan???
Decorating By jewlsjahl Updated 22 Mar 2009 , 8:05am by ClassyMommy
I'd recommend using any of the chocolate variations of the WASC cake recipe as it always comes out moist. 
Here's a thread on stacked/tiered/layer cakes that has both versions of the WASC cake recipe (with and without oil/fat) and chocolate variations:
http://cakecentral.com/cake-decorating-ftopict-605188-.html
Another chocolate variation by Cakepro:
http://cakecentral.com/recipes/7367/amazing-chocolate-wasc-cake
The above thread also has links to Wilton's cake preparation and servings guide which gives batter requirements by pan size and recommended baking temps. and times.
A 12x12x3 pan takes 14 cups of batter (per layer) - so a full recipe of the WASC should work out perfectly for you. I'd also use either inverted flower nails or a baking core and bake-even strips to help the center bake while preventing the edges from becoming over done (both discussed in the above thread).
Good luck!
HTH
P.S. Investing in a separate oven thermometer to make sure your oven is baking at the right temp. is also a worthwhile investment.
I would agree with JanH. If you use a WASC chocolate cake recipe you will have better luck. Just in case you don't already know, that is a doctored box mix recipe where you add to the box mix. Also, the bake even strips can just be a cut towel that is damp with water and hooked to the outside of the pan. (Can be with a binder clip)
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