Mashed potatoes cool down quickly, so you usually whip these up last. But, sometimes I mis-figure the time & like this evening, I had my potatoes done way too early. So I put my mashed potatoes into my 7X11 pyrex dish, dotted them with butter, sprinkled on a little parsley (this is optional), & stuck them in the oven at 225 to just keep them warm.
Here they were before going into the oven to keep warm.
And here they are about 15 minutes later after coming out of the warm oven when the rest of the meal was finally ready.
I reckon you could just use the microwave (especially in the summer), but the warm oven does truly keep them warm at an even temperature.
Trick #2 for this is to use your crock pot. I only do this for big dinners like Thanksgiving, but I'll make my mashed potatoes about 30 minutes before serving dinner & then put them on low in the crock pot. This keeps them warm while I'm busy doing other last minutes things, like turkey gravy or noodles. Just don't forget to turn the crock pot off when people start filling their plates, or right after dinner.
You can see more Kitchen Tips over at Tammy's Recipes!