When I was a kid, it was a mortal sin to have lumps in your mashed potatoes, and one of the solutions was to get out the electric hand mixer and whip the crap out of those poor spuds. This paved the way for instant mashed potatoes, which were never lumpy, but seldom tasted like real potatoes because something is lost in the processing. After all, the potatoes are cooked, mashed, and then dried, so that's got to take a toll on flavor.

Wikipedia says: "Flaked instant mashed potatoes are the most common found in the local US/Canadian stores. Granulated or Potato Pearls are generally reserved more for institutional or restaurant use. Granulated mashed potatoes can be found in some wholesale clubs or are available through those that carry dehydrated or survival foods. Unlike the flaked mashed potatoes, both of the granulated and pearls will be more hygroscopic when it mixes with water. They will generally have an improved flavor, higher yields, and a firmer mix, in that regard."

Then, maybe 10 or 15 years ago, there was a food revolt, and it became the style to once again make the mashed potatoes from fresh potatoes, and a few lumps were okay, in fact desirable, to prove the potatoes were 'real.' So once again it was okay to own a potato masher. Another way to mash them is to use a potato ricer or a food mill where the cooked potatoes are forced through small holes. No lumps there. And there is always the electric mixer.

This is a Foley food mill:


I bought a potato ricer, but don't like it very well, too hard to clean, doesn't hold much at a time, too much force required to push the potatoes through, and that's all it's good for, unlike the food mill which can be used for a variety of foods.



Here's Julia Child with a ricer she bought in Germany in the 1950s. Her Smithsonian website claims she stopped using it when she bought a big Kitchenaid mixer, but I'm not sure I believe that because this ricer looks so nice, and it comes apart for cleaning.



My recipe for mashed potatoes, generally using the food mill, but I sometimes use the potato masher:

Mashed Potatoes

Russet or Yukon Gold potatoes, cut in chunks
Cold water to cover
Salt

Butter
Chicken broth or milk or cream or a combination, heated in microwave
Salt
Pepper
More butter for serving

Cook the potatoes until very tender. Peeling them before cooking is optional. When done, dump them into the food mill set over a bowl (save the potato water for making bread or rolls). In the cooking pan melt a couple tablespoons of butter. Crank the potatoes through the food mill directly into the saucepan and cook over medium heat for a few seconds to dry off any moisture. Stir in the butter and then the hot liquid, a little at a time to get the texture you like and season with salt and pepper. Serve immediately, or cover the top of the saucepan with a clean kitchen towel and set it over another pot of hot water, and cover loosely with a pan lid. Don't shut it up tightly because it will develop an off flavor. When ready to serve, pile the mashed potatoes in a heated serving bowl and make a crater in the top of it, like a volcano. Put a good-sized pat of butter there to melt and make a couple of little breaks in the sides of the crater for the butter to run out onto the slopes.

The only difference when you use the potato masher is that you go at the drained potatoes in the cooking pot with energy, pushing it down then pulling it toward you. Stir in the butter and hot liquid.

You could also get out the hand mixer and beat the crap out of the potatoes, adding the hot liquid and butter as you go.

There are recipes designed for making the potatoes far ahead of the meal, containing additional ingredients like cream cheese. I've posted one here somewhere.