Empty the cold mashed potatoes into a medium saucepan or Dutch oven and set over low heat. Cover the potatoes and stir them occasionally until they are completely warmed through and smooth. Be sure to keep the heat low and stir, otherwise the potatoes may start to stick to the bottom of the pan and scorch.
Cover with aluminum foil to keep the potatoes from drying out. Reheat at 350˚F for 20 to 30 minutes, or until the potatoes reach 165˚F.
Reheat in the Oven
Whether they're made with just potatoes, milk, butter, and salt or jazzed up with ingredients like sour cream or garlic, mashed potatoes will heat up wonderfully in the oven.
Usually, restaurants reheat mashed potatoes inside the crockpot for several hours. If you also want to try using this method at home, be mindful of signs of spoilage such as changes in texture or color when keeping it for long hours. Also, check the temperature setting when you reheat the dish to avoid overheating.
Whether reheating leftovers or using a recipe to make mashed potatoes ahead of time for a crowd, warming those spuds in a double boiler will do the trick. Alternatively, you can place your potatoes in a Pyrex glass bowl set over (but not in) simmering water.
Mashed potatoes can be kept warm in a crockpot (if serving later the same day) OR refrigerated for up to 2 days. To reheat, place them in a large pot over medium-low heat, stirring constantly and adding additional milk/cream as needed to achieve the desired consistency.
Spoon the potatoes into the serving dish, if you are serving the dish family style. Use the back of the spoon to smooth and round the pile of potatoes. If you are plating the potatoes in the kitchen, leave them in the mixing bowl or pot and cover the bowl with aluminum foil until you are ready to serve.
If you refrigerated your mashed potatoes in an oven-safe casserole dish, set them out on the counter to take the chill off for at least 20 minutes before you pop them into the oven. When you're ready, bake, covered, at 350 degrees for 15 to 20 minutes, or until the potatoes are hot throughout.
Too much heat and you'll dry your potatoes out. Too much moisture and they'll turn to glue. The directions below, which are similar to reheating stuffing in the microwave, work well in most situations. But they will need to be adapted based on your microwave power and how much mashed potatoes you're reheating at once.
Instead, seal your fully made mashed potatoes—cream and all—in a vacuum bag, and keep them warm using an immersion circulator until ready to serve. At this point, immersion circulators are affordable enough to make them a viable option for many home cooks.
If food has been hygienically prepared, cooled quickly after cooking (or reheating) and stored cold, reheating more than once should not increase the risk of illness.
How Long You Can Keep Leftover Mashed Potatoes. Mashed potatoes should easily last three to five days in the fridge if stored correctly and within two hours of cooking. This means ensuring there isn't any moisture buildup under the lid that could encourage the growth of bacteria.
Mashed potatoes can sit out for two hours at room temperature. Any longer than that, they can enter the “danger zone,” which are unsafe temperatures that promote the growth of bacteria. If temperatures go above 90 °F, mashed potatoes can only sit out for one hour.
Keeping your mashed potatoes in an airtight container will keep them fresh for longer, and prevent them from absorbing smells from surrounding food, per The Rusty Spoon. They state there are a few telltale signs that your potatoes have gone bad. The first and most obvious is moldy patches.
Previously cooked and cooled Time/Temperature Control for Safety (TCS) foods that will be HOT HELD must be reheated as follows: *All parts of the food must reach a temperature of at least 165°F for 15 seconds.
Texture: Texture is another sign of whether mashed potatoes have gone bad. If the mashed potatoes are slimy or have a watery consistency, they should be discarded. Additionally, if the mashed potatoes are hard and dry, they may be stale and not suitable for consumption.
Mashing potatoes ahead of time
In fact, if reheated in the microwave with a bit of extra butter, your favorite starchy side may taste even better the next day. Or you can dollop in a supercreamy mixture of butter, half-and-half, and sour cream to keep pre-mashed spuds from drying out.
Never try to mash up cold potatoes. It has to do with some chemical-y thing with the starch. If your potatoes go cold, heat them up again (in warm water, a microwave) and then try to mash them.
The whole process is simple: peel them, leave them whole or dice them if you want, fill a bowl with cold water, submerge the potatoes and store in the fridge overnight. While this trick can be quite handy, it will only work for about 24 hours, so we would recommend to not prep your potatoes too far in advance.
As soon as you peel the potatoes, you'll want to place them into a bowl of water so they're fully submerged, and then store the bowl of potatoes and water in the refrigerator. The water will seal off the potatoes from the air, so the chemical reaction can't occur. Pretty smart.
Season with salt and pepper. Plan on 1/3 to 1/2 pound potatoes per person for your feast.
Test Kitchen Tip: You can boil potatoes ahead of time for use later as long as you cover and refrigerate them. They'll last for up to three days in the fridge.
How Long Can Boiled Potatoes Sit Before Mashing? If you want to boil your potatoes in advance of mashing them, leave them sitting in about 1-2 inches of the cooking water for up to 2 hours. Then when it's time to mash them, you can bring the water to a simmer to reheat the potatoes.
Reheating mashed potatoes in a slow cooker or Crockpot ⇢ Making use of a slow cooker or Crockpot is a great option if you're low on oven space on Thanksgiving Day! Transfer the potatoes to your slow cooker & reheat with the low setting for 3-4 hours. Check the Recipe Notes, below, for more guidance!