Ingredients

• 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
• 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

Instructions

1. Purée chives and parsley with oil and salt in a blender until smooth. Pour herb oil through a fine-mesh sieve into a glass measure, pressing on and discarding solids.
2. Prepare potatoes: 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.
3. 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.
4. While potatoes are simmering, bring milk, butter, salt, and pepper just to a simmer, stirring until butter is melted.
5. 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.
6. If desired, serve potatoes drizzled with some of remaining oil.