FOR CHIVE AND PARSLEY OIL
- 1 cup chopped fresh chives
- 3/4 cup chopped fresh flat-leaf parsley
- 1/2 cup plus 3 tablespoons olive oil
- 1/4 teaspoon salt
FOR MASHED POTATOES
- 5 lb yellow-fleshed potatoes such as Yukon Gold
- 1 1/2 cups milk
- 1 stick (1/2 cup) unsalted butter, cut into tablespoon pieces
- 1 1/4 teaspoons salt
- 3/4 teaspoon black pepper
Peel and quarter potatoes. Cover potatoes with salted cold water by 1 inch in a 5-quart heavy pot, then simmer, uncovered, until very tender, about 25 minutes.
While potatoes are simmering, bring milk, butter, salt, and pepper just to a simmer, stirring until butter is melted.
Drain potatoes in a colander and return to pot. Add hot milk mixture and mash with a potato masher until almost smooth, then stir in 4 tablespoons herb oil.
If desired, serve potatoes drizzled with some of remaining oil.