Save cooking these for the end of the preparation process, about 30 minutes before you eat. I think the plain, brown-skinned mealy potatoes called russets mash up best, but this is an individual choice. Remember, they’re going to be swimming in gravy anyway.
Peel a mess o’ spuds (at least a half pound per head, more if you’ve got big eaters), cut into roughly egg-sized pieces if necessary, and put in a big pot with enough salted water to cover. Bring these to boil, but don’t ignore them. Potatoes cook pretty fast, and you don’t want them overdone.
When they pierce easily with a fork, they’re done. Remove from heat and drain, then put them back on the heat briefly to drive off any excess water. Add a good chunk of butter (more is better), a splash of buttermilk (or cream or half and half), and mash. I like mine a bit chunky and use a plain wire masher (cheap at any supermarket).
Some people rice their spuds, others use a mixer. Don’t, under any circumstances, put them into a food processor or you’ll get something resembling wall paper paste.
Just keep mashing and adding a bit of buttermilk (okay, you can use any milk, but buttermilk adds a nice flavor and creamy texture) until they look good. Cover and set in a warm place. Dinner is not far off.