Microwave in a covered microwave-safe bowl
Add a splash of milk, cream, or butter before heating
Heat in short intervals, stirring between each
Stovetop in a saucepan over low heat
Stir frequently to prevent sticking or burning
Add a little liquid if the mash is too thick
Oven in a covered baking dish at low temperature
Stir once or twice while heating
Use a double boiler for gentle reheating
Reheat until the center is hot throughout
Do not overheat to avoid drying out the mash