Ok, tried to do a half dh yellow and dh devils food cake in a 11 x 15 pan. The baking  times were off by 2-3 minutes on box, so I thought I would be ok, but when I cooked them the yellow baked fine but not the chocolate. Still not cooked through in center. Used two flower nails evenly spaced in middle of pan. Temp set for 325 and baked for 46minutes. The recipe I used was a doctored Wilton recipe (dream whip). Any suggestions. I would even do the dh yellow cake made into chocolate if possible using this recipe so they would bake the same. I did try just adding cocoa powder to a dh yellow cake mix,but it tasted terrible on my trial cake.  Saw on an older forum.  Any help is greatly appreciated as I am new to this. 

The recipe that is used is:

dh mix

envelope dream whip

4 eggs

cup milk

Are you baking them in the same pan?  When I do a half 'n half...I bake separately...2 quarter sheets and put together on the board to make the half sheet. 

I wanted to make in same pan since I don't have other cake pans. Trying to avoid having to purchase more pans. Thought about putting nails on chocolate side instead of yellow batter side to see how that would bake but I hate to have to make yet another cake. I have noticed a lot of people using your idea and may have to do that if no other suggestions.  Thank you for replying!

It might be better if you were do seperate sheet cakes for each cake flavour, cut them in half, and perhaps freeze whats left over for another day. It can  be difficult to cook both mixes together-  due to the fat difference in both recipes. Chocolate cake can take longer to cook, than a plain cake due to its higher fat content - as in the cocoa powder or cooking chocolate.

Hope this helps!

I would say bake 2 cakes.  Use the same pan for each one.  I did that for a sheet cake.  The only problem I had was making sure the seam between the 2 cakes was not visible.  I won't be doing that again, though.  It took awhile to get it right.

Ok, if I want the cake for Saturday afternoon and my original plan was to decorate Friday so it was ready early in case i have problems.  If i piece cake together, will the cake dry out because it has been pieced together and decorated the night before or will the icing seal the moisture in the cake like normal? Sorry so many questions but this is the first time making such a large cake and I don't want to make a mess of it.  My schedule was going to be make today and freeze then take out on Thursday to thaw then decorate Friday in the pm. Again, new to this so I used a combination of ideas I read on different forums. Of course, I welcome any suggestions,:)

You'll be fine.   Also,  I always trim the two center sides that will touch so it is cake-to-cake touching.   I also take some of my cake top and fill in the gap that you will have running down the center.   You will also need to use a cake "drum" or a sturdy board.   The first time I made my half 'n half cake like this it would crack down the center when I was moving it in and out of the frig.    All of my full sheet cake orders are 2 half sheet cakes put together.   I seam 2 cakes together very often.  

Ddaigle, thank you very much!  I'm nervous since this cake is for a friends husband and I have only made cakes a few times for family. Do you put icing in between middle where they touch, like some do?  Not sure i like that idea unless you think it will hellpmfor movement. Also is there a good size cake board or " drum" you would recommend.  I have a 16 inch thick cake board but can't find bigger in store but could try online.   Again, thanks!!!

I think you are doing a half sheet cake?   Just use a  half sheet size board.  It's the thickness of the board you need to concentrate on.  Hopefully your local party supply store sells them.  They are 1/2" thick.  They may have other board options there for you.  

I don't put a lot of butter cream down that center seam..but I do put some..   You are going to have an indention where the two cakes connect sorta like if you were making a book cake.   I just put on my #12 tip and run a thick tube of icing down the center of that crack..then cover with a cake scrap for the top I cut off.   I also would not worry about trying to cut 2 strips of each cake flavor.  That crease is not big enough when cut to worry about.   Just pick one flavor and cover that seam.  

For sheets cakes I usually have the larger cake boards custom made from "cut offs" of  LAMINATED chipboard,  Its advisable to place two shorter lenghts of 2"x1" timber underneath - raising the board up makes it easier to lift the cake. Covering the board with fondant, and the edges with ribbon will give it a more professional look. Good luck and happy baking!

Hope this helps!

Thank you for all the information and help I really appreciate it!

I have done SEVERAL half and half cakes and ive never had more than a few minutes differece on the cook time. i only use Pillsbury cake mixes (not sure if that matters) the only time i dont use them is if they dont have the flavor i need. make sure you follow the direction on how many cups to put in your cake pan. if you over fill it or have to much on one side that could definatly affect your baking times. when doing a split cake I measue the batter out first and i do not "Guestimate" Hobby lobby sells a cake "divider" you can put in the pan while pouring the batter. If you use Hobby Lobby's 40% off coupon you can get it for about 5-6 dollars. The advantage to this seperator is that if you see your "seam" is not in the middle you can use it to adjust your center. Once your mix is centered you take the divider out before baking. cook at 325 and it will most likely take 50-60  minutes depending on your oven. Hope it goes well for you.

Wow Connie...that gadget sounds neat.   I thought I had everything Hobby Lobby made.  Sounds like a road trip is due!  Thanks!

lol its not without its qerks. its easier with two people pouring the batter but if your alone you may need to use clothes pins or those black paper camps to hold it I place it has a tendancy to move during the initial pouring.:(