Low Fat Mashed Potatoes

1 1/2 pounds russet potatoes, peeled and cut into 2-inch pieces
1 tablespoon olive or canola oil
3 tablespoons reduced-fat sour cream or plain nonfat yogurt
1/8 teaspoon salt
1/8 teaspoon freshly ground pepper

1. Place potatoes in a large saucepan and add enough water to cover. Bring to a boil over medium heat and simmer until potatoes are fork tender, 20 to 30 minutes.
2. Drain potatoes, reserving 1 cup cooking liquid. Press potatoes through a ricer or mash in the saucepan. Stir in oil, sour cream, salt, and pepper until well blended. Gradually stir in some of the reserved cooking liquid until the potatoes become creamy and smooth.