I promise this is a proper cake, not a bread, though it uses elements of bread and cake baking. It has a full flavor and mild tartness from the sourdough, but the crumb and sweetness of cake. It's full of whole grain, but is not dense or gummy. Laced with cinnamon-sugar walnuts, this is the perfect thing to accompany of cup of coffee/tea and a good book.
I was inspired by a bit of history from Zingerman's Bakehouse, where they mentioned cakes were yeasted and sour cream was commonly used instead of milk before chemical leavening and refrigeration were all the rage. As much as I love the convenience of modern life, I went full on DIY and made a naturally leavened cake. While I was re-inventing the wheel, I used sourdough starter instead of sour cream to bring the tang to this cake.
The cake uses a common technique in bread baking: a preferment. The preferment lends robust rising power (and good flavor), which is important for the cake to rise in a timely manner once all the butter, sugar, and eggs are added. It also has the added bonus of giving the microbes a head start in fermenting the whole grain flour and not just the sugar added later, releasing more nutrients for us. Be sure your starter is freshly fed and active; I’ve seen other cakes use discard starter primarily for flavor, but we need that rising power here too. As insurance, a little bit of osmotolerant yeast is added later on in the cake.
A note on hydration and flours: I use fresh milled flour for this cake, aiming for a 50/50 blend of low and high gluten grains. I’ve used 25% Sonora wheat, 25% Einkorn, and 50% hard white wheat, or subbed 25% spelt instead of Sonora, with good results. But following this exact blend is not necessary, it’s more important to get the right consistency. There’s a lot of variation between grains and their ability to absorb liquid. This is where bread making intuition comes into play. Depending on the type of flour used and the hydration of your starter, you may have to tweak the amount of liquid added to the preferment. It should be full hydrated (no dry flour), but firm. Experiment with different grains, have fun with it! It’s not necessary to mill your own flour for this cake, but it is designed for whole grain flours. —Stephanie B.