The Food Lab: Better Home Cooking Through Science

significantly sweeter and more flavorful than the plain
roasted potatoes, which were starchy and bland.
Interestingly, the hour-long-parcooked potatoes were nearly
as flavorful as the overnight potatoes, which means you’ve
really got to cook them for only an hour at 150°F.
If you’ve got a temperature-controlled water bath, the
path to better sweet potatoes is an obvious one. Just bag
your potatoes, cook ’em as long as you’d like at 150°F (any
higher, and I found they softened too much before
cooking), and then pop them into in the oven while your
turkey is resting.
For the rest of you, there are a couple of options. You
could always go the beer-cooler sous-vide route outlined
here. It’s cheap and effective, and it will easily hold the
proper temperature for the requisite hour. Just put your
potatoes in a zipper-lock bag with the air squeezed out, then
put them into a cooler filled with water at 150°F, close the
lid, wait an hour, and you’re ready to roast.
The good thing about sweet potatoes is that they’re less
finicky than, say, a steak, which means that you don’t have
to worry about getting the temperature exactly right. In fact,
as long as your water’s above 135° and below 170°F, it’ll
have a positive effect on their sweetness.
Don’t want to use the cooler? Here’s an even easier way
to do it: Bring 3 quarts of water to a boil in a large pot. Add
4 cups of room-temperature water. This should bring your
water down to around 175°F. Add a few pounds of sliced or
diced sweet potatoes to that water, and it’ll come down to
well within the requisite range. Pop a lid on the pot, put it in
a warm part of your kitchen, and leave it there for a couple