Mashed Potatoes With Chimichurri Butter

Place potatoes in a large saucepan; add water to cover by 2 inches. Bring to a boil over medium-high; cook until potatoes are very tender, 13 to 14 minutes. Drain and return to saucepan. Add milk and salt; mash with a potato masher until smooth.

Pulse together parsley, cilantro, oil, vinegar, and garlic in a food processor until very finely chopped. Transfer mixture to a small bowl, and stir in softened butter until combined. Measure 3 Tbs. herb-butter mixture into a small bowl; stir remaining herb-butter mixture into mashed potatoes in saucepan. Transfer mashed potatoes to a serving bowl. Swirl reserved herb-butter mixture into top of mashed potatoes. If desired, sprinkle with crushed red pepper.