3 Yukon Gold potatoes, peeled and quartered
1/4 cup sour cream
Cover potatoes with salted water and boil until tender, about 20 minutes. Drain in a colander set over a bowl, reserving cooking liquid, and return potatoes to pot. Mash potatoes with 1 1/4 cup cooking liquid and sour cream. Season with salt and pepper to taste.
Note: for a different texture, scrub potatoes quarter but don't peel. Mash the peels in with the rest of the potatoes.