1. Put potatoes in large saucepan with water to cover. Heat to a boil over high heat; cook until potatoes are just tender, 8 to 10 minutes. Drain well and set potatoes aside. Wipe out pan.
2. Heat oil in same saucepan over medium-high heat. Add lemongrass and serrano peppers. Cook, stirring until slightly softened, 1 minute. Remove from heat; transfer to large bowl. Add yogurt, coconut milk and salt.
3. Quarter potatoes and add to bowl along with onion and cilantro. Mix lightly. Serve at room temperature. Nutrition