First things first, you'll want to make sure your mashed potatoes are stored in an airtight container in the fridge. This will help keep them fresh for a few days, and when you're ready to reheat, simply scoop out the desired amount and pop it into the microwave or oven. Easy peasy, right?
Now, I know what you're thinking: "But won't they be all dry and gloopy?" Fear not, friend, because with a little bit of cream or milk, you can revive those potatoes to their former creamy glory. Just add a splash, stir, and voilà!
methods to keep in mind when reheating your mashed potatoes. For example, if you're using the microwave, be sure to cover the dish with a paper towel to prevent splatters. And if you're using the oven, a low temperature and some foil covering will do the trick.
Can You Reheat Mashed Potatoes In The Oven at Amy Palmer blog