AHello hello :-)

So I just started doing big projects with cakes and decorating, and a family friend wants me to make a cake for a party. She wants a half sheet (12x18, yes?), half chocolate, half vanilla, with chocolate mousse filling.

What do you think is the best way to go about it?

I've been considering making 2 13x9 cakes, one in each flavor (slicing them horizontally and filling with the mousse) - and then placing them side-by-side to get the 13x18 overall size - But I am worried the two flavors will separate under the icing and it will fall apart in the middle through the icing and everything.

Then I considered buying a 12x18 pan, making the two-flavors in one pan, and then repeating the horizontal cutting and filling - but I am concerned the top layer will fall apart as I'm trying to remove it to fill and then placing it back on top. (Will I need to use flower nails/heating cores with this method? How do I do that with the two flavors?)

Agggghhhh!!

Any advice is greatly appreciated! :-)

I use a cookie sheet with a flat side to slide the torted half of the cake off & then back on after I fill the cake.

I also reduce my temp to 325 and use bake even strips.  I don't use a flower nail.

LOL  It's me again.  I bake in the same pan & don't do the two 13X9's.  OK !!  I'll shut up now!!

I've done the two 9x13" cakes many times. Yes use the bake strips if you have them or try  putting  your batter in the prepared pans and let sit on the counter for at least 30-45 minutes before placing in oven at 325 degrees.  Letting them sit out helps form a crust which helps the cakes raise evenly. You want to make sure the cakes are the same height.  Fill your cakes then spread a little frosting between the two 13x9 cakes to help hold them together.  Make sure you have your cake on an extra thick board, this helps it not split when picked up. If you are worried about spreading crumbs between the two different types of cake use an icing tip to apply your frosting this will help eliminate pulling cake crumbs between the two.

two 9x13s make for a big cake.  Do they really need that many servings?

I have often baked two flavors in my 12x18 pan.  You can make a divider by covering a piece of cardboard *exactly* 9" long (x2" wide) w/aluminum foil and wedge it into the pan.  Make your 1st batter and pour into pan; do the same w/the 2nd flavor.  Now pull the cardboard out and the two flavors will flow together &  bake up together as one cake.

As for torting that size cake:  use your cake saw to split it, chill well (even freeze the cake for a few hours), then slip a cakeboard between those two pieces to lift the top off and replace once the cake is filled.

Another option if your filling is smooth (such as a pudding based or frosting) is to put the filling in a cake bag w/a round tip such as a 3 thru 7 and inject it into the cake:)

Just push the tip into the cake about 1/2 way (so the opening is burried in the cake) and give it a healthy squeeze - repeating about every 2" all over the cake.  Works great and you don't have to worry about large cakes breaking into pieces. 

AI think the easiest and simplest way is just use the 2 9x13s, don't you?

I use my 12x18 all the time to carve shaped cakes from, and it does come apart quite often, but I just place the chunks where they go, and the filling holds it all together and then I ice it, and no one is the wiser. Sometimes I will go ahead and cut it if it is falling to pieces. No biggie!

I do them in the same pan all the time. I used to use the divider method, but unless your cake batter is uber runny, you shouldn't even need to do that. Just pour it on each side, and balance it out. 

AThanks so much for all the tips and input! I bought a 12x18 pan and an edge-less cookie sheet todsy to try that method first. I'm sure I'll use them in the future for other projects even if it doesn't end up working for this particular one. I also grabbed some bake even strips. I'm really hoping this works, but if not, I still have my backup 9x13! Haha

There were some awesome tips here - I'm very excited to try them! Thanks :-) :-)