How do I make an 11 x 15 cake half chocolate and half yellow?

I make the yellow batter [ mix or scratch..which ever you like] and tilt the pan so I can add the first 'color' of cake....leave it propped up and prepare the chocolate and pour it in the second side. I like to run a blade thru where the 2 flavors meet and make a 3rd flavor...MARBLE!

I fold up a pice of foil and lay it in the middle and pour one flavor on one side and the other flavor on the other side, then pull the foil out and the two flavors meet in the middle without mixing~

I do this all the time, I use a cardboard cake circle board that is cut in half. I cover it with foil and push it down in the cake pan. I have both cakes mixes all done and I have handles on my bowls too. Sometimes you have to hold the cake board in case it falls over. When you get both poured in just lift out the cake circle. I store mine and use them over and over. You must get a cake circle that is long enough to make it across the cake. Sandy

I do the foil like KHalstead --

but then I purposefully take a knife and swirl where they meet to make a section of marble cake.

I always just have the 2 batters ready at the same time and start pouring them in at the same time in the center. I don't use anything else. It works great as long as you don't mix them!

I do it just like bisbqueenb explained.
K

I have the 2 batters ready at the same time and I put una big spoon of one flavor and another big spoon of another flavor, if I am doing a marble cake, but if I am doing two separates colors, I baked in separate cake pans.

A friend told me to do it the way jenbenjr said. It works and is so easy. I never would have thought to do it that way!

wow! thanks for everyone's response...my friend wanted a "1/2 sheet" cake so I was just going to do a 9 x 13 pan chocolate cake, then a 9 x 13 yellow cake and put them together to make the 1/2 sheet. Do you think that will work?

That will work, but when I used to do it that way, the only problem I ran into was that the cakes weren't even. I was able to see the ridge between the cakes.

She is right about them not being level. If you cut the edges where you join them helps some. Sandy