Why is it so much more complicated to do a chocolate version of a standard yellow layer cake? That’s what readers Cynthia, Bertie, Doug and Seth all want to know. Why, if you’re converting a yellow cake to a chocolate cake, can’t you just swap out some cocoa powder for some of the flour and be done with it?
A chocolate cake layer certainly starts that way, Cynthia, Bertie, Doug and Seth, but cocoa powder turns out to be rather tricky stuff, chemically speaking. First, because it’s a fermented product, it’s acidic. So one must correct for that by adding an alkaline, otherwise the acidity would undermine the structure of the cake and make it softer (we especially don’t want that with the high ratio cake we have going here, because one of the virtues of high ratio cake is it’s firmness).
For this recipe I’ve added baking soda, which serves a dual purpose. Yes it counteracts the acidity, but it also gives me more leavening which is important since the cocoa weighs the cake down a bit and, not having any gluten in it or gelating starch, undermines the structure some as well. So we need the extra push to give the cake the right amount of volume. Cocoa powder is also extremely absorbent, so we have to boost the liquid content of the cake to account for that.
Lastly as I mentioned, the full flavor of cocoa powder isn’t released unless it’s combined with hot water or milk. So that adds a process step or two to the recipe, what with all the heating, whisking and cooling.
So there you pretty much have it. The chocolate high ratio cake recipe is basically the same thing as the yellow high ratio cake, save for all the balancing that needs to be done. It looks a lot different to be sure, but getting from one to the other really isn’t all that hard. Thanks for the question, guys!