Directions

1. Chop each potato into sixths or eighths, trying to keep the pieces about equal in size. Add these to a pot, along with the water and 2 teaspoons salt. Set on the stove over medium-high heat to come to a boil. Cook the potatoes for 10 to 15 minutes, until you can easily break apart a piece with a fork.
2. When the potatoes are cooked, drain them, then add them back to the hot pot on the stove, but with the heat off. Mash the potatoes with a masher (or, if you don’t have one, a big fork), until they’re as broken down as possible. Add the melted butter and stir until smooth-ish. Add the milk and stir again. Now add the vinegar and remaining ½ teaspoon salt. Stir, then taste. More salt, vinegar, or butter? More milk to thin out? Adjust accordingly.
3. Serve immediately with a pat of butter and flaky salt on top. You can also keep these warm on top of a double boiler, or reheat them (adding more milk as needed) just before serving.