Pronoun Trouble

Yup! Shoelaces3 there is basically describing how to make a "sour" 😀 It's one of the oldest types of leaveners (things that make bread rise), and has been used for millennia. These days it's mostly associated with sourdough bread, and is how said bread gets its tang. I hadn't heard it could be done with fruit skins or dried fruit, but I suppose it makes sense; I'm mostly aware of the "Just mix some flour and water together and then wait" method of sour-making. Yeast is everywhere and will grow wherever it finds a place.

It's a bit more work than I'm particularly interested in going to, I think, especially with the regular upkeep involved, but it's definitely an option!