Whether you want to keep freshly made mashed potatoes warm before serving them or you plan on serving leftover potatoes from the fridge for dinner, warming and rewarming them work equally as well in the microwave, on the stovetop or in a slow cooker. Even if you have just a small dab of leftover potatoes, save them in the refrigerator for up to four days to use in soups and stews.
Zapping in the Microwave
Microwaving allows you to warm mashed potatoes quickly without using a burner on your stovetop, freeing up the stove for other uses. The trick to reheating the potatoes is using a large enough bowl so you have plenty of room for stirring two or three times during heating. Warm the potatoes on medium high, for about 8 minutes for every 2 1/2 pounds of potatoes and add a dab more cream or milk if the potatoes seem dry.
Warming Gently on the Stovetop
If you have ample space on your stovetop, a double-boiler keeps mashed potatoes warm gently, with no risk of them drying out. If you don't own a double-boiler, make one by putting the potatoes in a heat-proof bowl, and covering it tightly with foil so steam doesn't get in. Place the bowl in a pot of water heated to just below the boiling point with the water coming up halfway on the sides of the bowl.
Reheating in a Saucepan
Reheating mashed potatoes directly on the stovetop works best if you plan to serve them right after warming. Use a large enough pot to allow you to stir easily and to add 1 to 2 tablespoons of milk or cream, and heat the potatoes over medium-low heat, stirring frequently. If the potatoes dry out, add more milk, cream or butter, 1 tablespoon at a time.
Warming in a Slow Cooker
Although you may never use your slow cooker for reheating, it does the job well when you don't have a microwave or room on your stovetop. Place the mashed potatoes in the slow cooker bowl and set the temperature on low. The potatoes will stay warm as long as the slow cooker stays on. As with other warming methods, add more milk or cream if the potatoes look too dry.
Putting Safety First
Reheating foods runs the risk of inadvertently providing a medium for bacteria to multiply. Play it safe with the mashed potatoes by checking their temperature with an instant-read meat thermometer. The potatoes should reach 140 degrees Fahrenheit after being in a double boiler or slow cooker and 165 F after microwaving. Insert the thermometer in the middle of the potatoes to get an accurate reading.