Use an immersion circulator to keep your freshly made mashed potatoes (and sweet potatoes) hot while you are busy cooking other dishes. Here are three things to keep in mind when using your immersion circulator to keep mashed potatoes warm.
Store the food in a container that makes for easy transfer into a serving vessel, such as a heavy-duty zipper-lock bag or a deli quart container.
Make sure that the potatoes are submerged in the water so that they will heat evenly.
Set the circulator to no more than 135 degrees and warm the food for no longer than 6 hours. We found that potatoes heated beyond that point or for longer turned dry. That’s because at temperatures above 135 degrees, the potato starches continue to absorb water, including water in the dairy added during mashing. As more and more water is integrated into the starch gel, there’s less free water to keep the mash moist.