In the last few years I’ve arrived at a conclusion regarding chocolate cakes, which I cannot prove scientifically, because I am not science-y, but it goes like this:
The best chocolate cakes all call for boiling or at least hot water. Could be hot coffee. Could be plain water. But there is liquid in the cake (not just milk or buttermilk) and it is hot.
Several times now, I have made recipes that call for this. Inevitably — and in every single case, I am not exaggerating — the resulting cakes are rich and moist (sorry, those of you who hate the word moist, but it’s called for here) and very, very chocolatey. They are perfect chocolate cakes.
The first cake I made a lot that called for boiling water was Aunt Velma. Aunt Velma is, as has been written elsewhere (https://longspaghettinight.wordpress.com/2013/03/01/aunt-velma-the-little-black-dress-of-chocolate-cakes/), is a perfect chocolate cake. It looks like a pain to make, but is in fact easily assembled in about fifteen minutes. I made it for various birthdays, for miscellaneous celebrations, and for no reason at all. It went well with every kind of frosting I ever had an interest in making, and was even lovely all by itself, unfrosted. It also keeps astonishingly well, not a normal or expected quality in a chocolate cake.
Then there’s this: http://theenglishkitchen.blogspot.com/2009/06/blog-post.html
This sour milk chocolate cake is one I turn to when I have sour milk in the house, which happens maybe once a year. Every time I bake this cake, I wonder why I don’t bake it more often. It’d be worth it to reserve some milk and let it go sour, just to bake this cake. (I think it’s silly to “make sour milk” by adding vinegar to milk, but I don’t mind the idea of making good milk go bad for baking purposes; this is insanity, but never mind.) And yes, the recipe calls for a small amount of hot water.
I am convinced, convinced, that what makes these cakes so good isn’t anything in particular except the addition of the boiling water. There are other recipes I’ve used that call for boiling water, too — these are just the only ones I can remember off the top of my head — but I’m telling you: If you are seeking a superlative chocolate cake, and you don’t have a fuckload of time to mess around with complicated processes but want something really rich and good, the thing to do is keep your eyes peeled for recipes that call for boiling water.
You will always want to remember to line your cake pans, if you plan to remove the cakes from the pans to frost and serve (these will be delicate cakes; you cannot remove an Aunt Velma from a 9×13 pan by just turning it out; you’d have to create a sling for it with tinfoil or parchment, and be very very careful). But I’ve done the sour milk cake in a nicely buttered Bundt pan with great success. These are flexible recipes, in terms of pans, as long as you are sensible and don’t do anything too crazy.
So remember what the Tante says. Boiling water. Someone else can talk science. I’m talking taste, and I’m not messing around. The JoC can keep its Cockaigne; I’m standing by Aunt Velma.