By any reasonable metric, this bread should have failed. From the very beginning, signs pointed to a miserable culinary defeat. For starters, it’s adapted from a recipe by Nancy Silverton called Pumpkin Bread. It has no pumpkin in it. Ostensibly, this is because she thought pumpkin bread sounded more appealing than yam bread. I disagree, having flipped over the recipe hundreds of times. And anyways, the vegetable commonly sold under the name yam in the US is not a true yam but a sweet potato, and sweet potato bread sounds pretty darn good to me.
The recipe also calls for you to cook 2 lbs of yams but you only require 10 oz for the bread for 2 loaves. I was able to get 14 oz of pulp out of 1 lb of cooked yam. What about the rest of the yams? Nancy gives no answer. I hope you have a sack. For yams. A yam sack.
Also! She called for whole wheat flour (do not have) and cumin (do not want). And there are two 6-10 hour retarding periods in the fridge instead of the usual one. Plus the dough is really wet and sticky and annoying to work with. And I forgot it on the counter until 4am. With all the tweaks, adjustments and mistakes I made, this should have been a terrible loaf of bread.

It was not a terrible loaf of bread. The crust is soft and the crumb was much lighter than I expected. Even using more sweet potato than the recipe called for, it didn’t taste as strongly as I had expected, but it added a nice complexity and made the house smell amazing.
Sweet Potato Bread inspired by Nancy Silverton’s Pumpkin Bread.
makes one 1.5lb loaf
8 oz of cooked yams (bake at 400 degrees for about an hour until soft)
6 oz of water
4 oz of starter
2 tablespoons raw wheat germ
12 oz white bread flour
1.5 teaspoons salt
Peel the yams and mash them with a fork. Let cool. Combine water, starter, wheat germ, yam, and flour and mix or knead for 4 minutes. The dough will be wet and quite sticky, if you’re doing this by hand, use a spatula. Add salt and knead for another 10 minutes, or until the dough is elastic and stretchy and can pass the windowpane test. I would post my own helpful picture here but this was a pretty messy dough and I didn’t want sweet potato chunks clogging up my camera forever. You understand, don’t you?
Put the dough into a well oiled bowl and cover with plastic wrap. Here is where I veer off course. Instead of refrigerating for the first ferment (6-10 hours), I forgot it on the counter. For about 8 hours. Fortunately for me, my sourdough starter is slow to rise to begin with and this dough with all the added sweet potato makes that process even slower. In the 8 hours, it just managed to double.
Too tired to fiddle with it, I simply moved it from the counter to the fridge. When I got up, I preheated the oven and took the dough out of the fridge to warm up again. Of course, it turns out that I had a dentist appointment that limited how much time I could let it rest, so I simply shaped it into a boule which deflated it quite a bit and threw it into the oven after about an hour. Fortunately, it was behaving appropriately, not quite bouncing back from my inquisitive jabs. After 30 minutes at 450°F, I had my bread.

Submitted to Yeastspotting
If you want to be less addle brained about this process, the recipe calls for 6-10 hours of fermentation in the fridge after kneading. Then you remove the dough, which should have increased in size by half, and let it rest at room temperature for an hour. Then you gently deflate and roughly shape and let rest for 15 minutes, after which you make your boule. Place into a proofing basket cover with plastic again and ferment for another 6-10 hours. Take the dough out and let it continue proofing some more until it increases in size by half again, then pop into the oven.
Or you could just wing it like I did.