in an old-fashioned country kitchen, brightly lit by sunshine, there's a large opened jar of fermented bread sauce with a spoon in it. the fermented bread sauce is a medium golden brown slurry. the sauce is used on a dish of cooked broccoli and fried mushrooms
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Isn't it essentially kvass? Or perhaps a cross between kvass and a sourdough. The only potential problem I can think of is that your kitchen is probably full of lacto-fermentation microbes that might compete with the yeasts if you don't start with an active ferment. Please let me know how it turns out.