Sourdough, attempt nine
Eight flat, dense bricks and then, finally, a loaf with an open crumb. The only thing I changed was patience: I let the dough rise until it was properly jiggly instead of pulling it early because I was hungry.
The numbers that worked, so I stop guessing: 500g flour, 350g water, 100g active starter, 10g salt. Four stretch-and-folds in the first two hours, then a long cold proof in the fridge overnight. Baked covered for twenty minutes, uncovered for twenty more.
The starter itself is the whole game. When it doubles in four hours and smells faintly of yogurt, everything else is easy. When it is sluggish, no recipe will save the loaf. I feed it now before I feed myself.