I was inspired by r0bz's question about sourdough cakes to try to make one. I used this recipe, but used sourdough instead of yeast: https://blog.ideasinfood.com/ideas_in_food/2013/02/yeasted-chocolate-cake-4.html
I omitted the yeast, added 100g of sourdough starter, reduced the milk by 50g, reduced the flour by 50g, and increased the milk powder by 5g. I used vanilla extract instead of paste, and I only used 1 1/2 tsps intead of the 40g because that is what my favourite baking-soda-raised chocolate cake calls for and I couldn't bear to dump a whole ~$10 bottle of vanilla into a single cake that was not likely to even turn out.
I just dumped all the ingredients together and mixed them with an electric hand mixer. I let the initial mixture sit overnight at room temperature instead of the 4 hours called for in the recipe. Then after mixing it up I did not wait an entire 18 hours, but I did put the batter in my dehydrator at 95F and it still took about 12 hours to double in volume and get very bubbly. Once in the pan, I let the mixture sit at room temperature for a few hours, but after no rise at all, I put it in my cold room overnight. The next day there was still no rise, so I left it out for another few hours and put it in the oven as soon as I saw a bit of rise.
The taste is okay. Actually, it's pretty good, but it is different. The texture is a bit dense and maybe even a bit dry, but it is a lot more delicate and airy than I was expecting it to be.
The recipe looks like it was originally a pound cake, and I think pound cakes traditionally don't actually include any rising agents except the eggs, so I'm not sure if you really even need to use yeast in such a recipe. I've never made a cake only risen with eggs before, though, so I don't know what it would be like or how it would differ from this.
Here's some photos, but I am very sorry about the crappy cellphone.
After rising all day at 95F the batter did not at all look bubbly like the photo in the recipe:
However, it had doubled in volume:
And, after stirring, the fermentation was much more obvious:
Into the pan. There was a LOT of batter:
Finally it rose some:
A miracle! It rose while baking:
It was tasty enough, but I probably won't make it again. I don't think it's actually as crumbly as this photo shows. Or at least, it wouldn't be if I had been more careful removing it from the pan. I had assumed it would be a sturdy lump, so I just dumped it out, but it was actually fairly delicate and cracked some which made it more crumbly after cooling.
