I was astonished to hear last week that people didn't know--well, some people didn't know--how to make mashed potatoes. In fact, the person who disclosed this to me was under the impression boiling potatoes and mashing them with your fork = mashed potatoes, and didn't understand what the fuss about them was. Well! Here's how one makes *proper* mashed potatoes, or the kind of mashies that taste wonderful, anyway.
Potatoes, peeled and diced (see picture).
Milk (preferably whole).
Salt (I use standard flavoured salt here, but if I
were at home I'd use plain iodised salt).
Wash the starch off the diced potatoes and put them in a pan with about an inch of water topping them, and set to boil. Cover, because they cook faster in the steam. After a few minutes put a fork through all the pieces to make sure the entire batch is soft and boiled. Drain. Now, using a fork or a mashing-thing, mash the potatoes. You can transfer them to a bowl before mashing if you like, but I don't bother, because it means more washing-up later.
Now, when the potates have been roughly mashed into a lumpy mass, add a dollop of butter. Blend this in well. Taste. If it isn't buttery enough, add more butter, and a little milk. Use your own discretion about the milk. Some people like their mashed potatoes tight and on the drier side, some people don't mind it moist. Blend in well, really giving the mashing-thing a go. The potatoes should no longer be lumpy, but a smooth melt-in-the-mouth mass.
Finally, add the salt and blend this in well to. I always add a smaller amount of salt than I think I will need, because you can always add salt after but you can't take added salt away. If you're heavy handed with salt, make sure you keep one or two diced pieces of potatoes aside. Mix them in only if the final mashies have too much salt. Sometimes though, even that won't cure the extra saltiness. So just be careful.