I have to make a marble cake for a wedding next month. I tried to make one, by just adding coco to about a third of the batter and swirling it though. But it didn't seem to be chocolaty enough.
I make a batch of yellow and a batch of chocolate, put one flavor on one side of the pan and the other on the other side then swirl with a knife to mix them,
I make a yellow cake (or whatever flavor, strawberry is good, too) and reserve a cup of batter which I mix with a 1/4 cup cocoa powder til it looks like choc. batter.
The rest of the yello batter goes into my pan and then I drop spoonfulls of the choc. onto the yellow and swirl with a knife.
I have only made marble cake in 11X15 pans, but I'm sure the process would be the same for any shape. I make yellow batter and put it in the pan first. Then I make devil's food and put it on top of the yellow. Then I take a butter knife and swirl all around. I think it makes a good combination and I have had many repeat orders for it.
Thanks so much for your answers! You guys are a big help!