Let me get this out of the way - it’s OK to use frozen or packaged or dried mashed potatoes. It is. They are really quite good. Plus, by the time you add a bunch of extra ingredients - even your grandmother couldn’t tell they weren’t from scratch. This is just a guide - you can add almost anything to mashed potatoes - goat cheese, sour cream, bits of roast beef, rice pudding, quickly sauted vegetables, crunchy rice noodles - by the way I was just kidding about the rice pudding.