I read
https://www.pizzamaking.com/forum/index.php?topic=35873.0 and watched all the videos I could find on this topic.
Here are the results of my first time baking with yeast water.
To make the yeast water, I put 100g of dates and 400g of water in a jar. I put them in the oven with the light on (86F) for 5 days, shaking them a couple times each day. At the end of the 5 days, the dates were all floating and the water was fizzing. I strained the dates and put the water in the refrigerator to wait for baking. The resulting water was quite sweet, so I would probably use fewer dates next time.
To make the poolish for my dough, I put 50g of the yeast water and 50g of King Arthur bread flour in a jar. I left it on the kitchen counter at 72F for about 21 hours when it had tripled in size and appeared to be at its peak. I did not do multiple feedings as I didn't want to turn this into a sourdough.
I made the dough as soon as the poolish was ready, using the following:
Flour (KABF): 436g (100%) - includes 50g from poolish
Water: 292g (67%) - includes 50g from poolish
Sea salt: 13g (3%)
Olive oil: 9g (2%)
I dissolved the poolish in the water and added about 75% of the flour and left it to autolyse for 30 minutes. I added the remaining flour in 2 parts, letting it rest for 20 minutes between each. Then I kneaded in the oil and continued to knead by hand until it felt "transformed". I let it rest another 20 minutes after kneading and it became extremely smooth, stretchy, and light in color, just what I wanted. I put it in a bowl to ferment at 72F.
My initial plan was to do the full rise at room temperature but I didn't know how active the yeast would be. Before going to bed, it was clear this was very active and would be overfermented if I left it at RT overnight, so I decided to ball it and put it into the refrigerator. In the morning I took the dough out of the refrigerator and put it in my garage where it was about 55F and by 7pm it was ready.
The end result was some of my best pizza yet. It was soft and had a lightly crunchy exterior. It was firm enough that it wasn't floppy in the middle, but it wasn't tough. The results probably had more to do with my improved kneading and fermenting process than from the yeast water. I didn't notice any distinct taste or sweetness from the yeast water. This was the desired outcome for me, as I like the idea of natural leavening but don't really appreciate the aftertaste of sourdough.