I would like to know how to make a sheet cake 11 x 15 half white cake and half chocolate cake ? I have never attempted this before and need to make this for a b-day party on Friday...
Any suggestions ?

A few different ways. I'll list several. Do whichever strikes your fancy best.

I think the most common is to just pour both batters in at the same time. Batter is thick. It won't really mix. It may just barely where it comes together.

OK- not straight enough line for you??

Insert a piece of folded heavy duty foil where the line should be. Pour in both batters. Remove the foil for minimal mixing and bake.

Buy a special pan divider made just for this (come on though, I'd rather spend my money on other fun things)

Bake 2 11*15's, one of each. Cut them in half. Spread a bit of icing on your cake board to use as glue (to keep the halves from shifting). Spread icing on one of the cut ends. Lay both ends together using the icing to glue to two halves together. Decorate as usual. Save the other halves for small dessert cakes, another combo cakes or small sampler cakes.

I find the first method to be best...Never made it myself, but when it's cut, your guest have 3 different alternatives ...Chocolate, marble (swirl the cake where they meet) and yellow...

I was pleasantly surprised once with a cake like this...Had a piece of yellow and when I asked for a second, I got a delicious marble piece

How did your cake come out???

Here's another easy way to make sure your cake is 1/2 and 1/2:

Lay out two kitchen towels, with the long edges butting up to each other. Put your prepared pan on top, with the towel "seam" under the halfway point. Try to keep the line as straight as you can. This will give you a guide for pouring the two batters.

I use two large (8-1/2 cup) handled measuring cups to pour the two kinds of batter, starting at the edge furthest away from me. Pour each batter as evenly as you can, moving your hands simultaneously along that "seam" until you get to the opposite edge. Now fill in the rest of the pan on each side of your cake "seam". This should result in an evenly baked and proportioned cake.

I have a lot of people who ask me for half-and-half flavored cakes and this method helps me to line up the batter so I have enough of each to accomplish what I need.

Good luck with your cake, and remember, this isn't rocket science ... anything you can dream up, anything you or your customers can imagine can probably be accomplished in cake!

My 1/2 choc and 1/2 white sheet cake came out great! I cut a piece of cardboard and covered it with foil to fit the inside of my pan. My granddaughter held it in place for me while I poured each batter then I pulled it out and it was great!

Here is how I do it all the time. I just bake 2 cakes, one white and one choc and then put them together. Most times I cut the edeges that meet. I do this all the time with no problems.