There are a lot of ways to prepare mashed potatoes, and almost all of them are valid (even, or especially, the microwave method). Most mashed potato recipes start the same way: Cube the spuds into roughly 1 1/2-inch chunks, then cook them in simmering water until they can be easily mashed with a fork. This usually takes about 20 minutes, but Cook’s Illustrated notes you can shave off half of that time by slicing the spuds into 1/4-inch rounds, rather than cubing them into chunks.
This move is quite obvious when you think about it: A thinner piece of potato will cook faster than a thicker one, and a uniform slice will cook more uniformly than a lopsided chunk. (There will, of course, be some irregularly shaped pieces taken from either end of the potato. That is the nature of things that grow in the ground.) Slices also take up less space, which means you use a smaller pot and less water (you just need enough to cover the spuds).
You can try out Cook’s Illustrated’s full recipe, which is easy to execute and flexible enough to allow tweaking, or you can lift the slicing trick out of the recipe and apply it to your favorite mash (even a microwave mash).
I do urge you to exercise a small amount of caution and care should you go this route. Getting mashed potatoes into your mouth quickly is a worthy endeavor and attainable goal, but not if all that haste makes them gluey. The longer you cook potatoes, the more starch you release, and the more likely that starch is to gelatinize and glom up your mash. Thinly sliced potatoes cook very quickly, so keep your water at a simmer, not a boil, and start checking after seven minutes or so. When you can easily pierce through the center of the potato with the tip of the pairing knife without any resistance, you’re done. Strain them, then proceed with your mash as usual.
