The beauty of mashed potatoes is in making them the day before and reheating.
I like to keep the pan of drained, cooked potatoes in the refrigerator until ready to reheat, mash and serve. The cooling of the cooked potatoes makes fluffier mashed potatoes. The starch molecules tend to explode when reheated, making a fluffier mashed potato. This way, they can be mostly made the day before. I have discovered the hard way that potatoes other than Russets or Yukon Gold tend to whip into a gloppy wheat paste of unappetizing goo. Get out that potato masher for best results or beat minimally with a hand mixer on very low speed.
3 pounds Russet or Yukon Gold potatoes
1 1/2 teaspoons salt
1 cup whole milk or combination with cream or half and half
¼ to 1/3 cup unsalted butter
White pepper and additional salt, if desired
→Peel potatoes and cut into 1-inch cubes. Place in a 3-quart heavy saucepan and cover with 5 cups cold water and salt, bringing to a boil. Reduce heat and simmer, partially covered, until potatoes are fork tender. (About 10 to 15 minutes).
→Drain potatoes in a colander, then return to pan and cook over low medium heat, stirring occasionally until cooking liquid is gone (about 2 minutes). Add milk and butter to the pan, reheating over moderate heat until butter is melted. Mixture should be steamy hot, but not boiling.