I fell down a Japanese bakery documentary video hole during Day Job Hell Season, during those times when I had a boring "sit at workbench and put lots of things together" stretch.
(Because y'all are going to ask, my favorite channel in this genre is Bread Story and this video is a primo demonstration of some of the absolutely bonkers ass things Japanese bakeries are doing with bagels these days)
One thing I saw a lot of in those videos was that a lot of bakeries use homegrown yeast from...... raisins. Raisins? Raisins.
In theory, it's pretty simple: you take a jar, and you put raisins in the jar, and you put water in the jar, and you put sugar in the jar, and you let it hang out on the counter for a few days until it starts fizzing. And then you strain out your raisins (and maybe put them in bread or something), and the liquid you're left with is chock full of live yeast that can then be used in your baked goods!
In practice it's... only a teeny bit more complicated than that, in that you have to get your ratios right or else you get mold instead of yeast. I found a tutorial at Sourdough and Olives that worked for me. I've made a sourdough starter before and honestly? The raisin process is SO MUCH FUCKING EASIER. You don't have to take out discard or feed it like... fresh raisins every day until it gets going. You just measure your stuff and put it in a jar and put it in a warm spot and make sure it's not growing fuzz and you leave that shit to its own devices until the yeast starts partying in there.
Really, functionally, it works a lot like sourdough starter except instead of a sour flavor, it's got a kind of sweet taste that's reminiscent of beer bread. Which makes sense, seeing as how the process of making raisin yeast is basically... prison wine, interrupted. Anyway, it doesn't taste fruity as such, but it definitely hits different than commercial yeast or sourdough.
I actually mixed all my yeastwater with flour and put it in the fridge like a sourdough starter and I maybe shouldn't have done that, but it does come back to life nice as you please when it comes to room temp and gets some fresh flour and sugar to munch on. All my raisin yeast experiments so far have involved making a levain (starter + flour/water/sugar) that sits overnight and it does seem to take a little longer to get in gear than commercial yeast, but once it does it works great.
I've been using King Arthur's Japanese Milk Bread Rolls recipe as a starting point--same bread recipe I used for that anpan a few weeks back--and it seems to adapt really well to the use of a starter. This week's experiment was an assortment of bespoke hamburger buns on which to slap my veggieburgers (plain, everything bagel seasoning, and cheese) plus two raisin buns. It works well for both sweet and savory breads. It makes a bangin breakfast sandwich. I haven't tried French Toastifying it yet, but it should work well.
And yes, I am absolutely going to try making some of those bonkers ass bagels. Mmm, misonegi.