• 1/2 cup unsalted peanuts
• 2 tablespoons chopped fresh basil
• 2 tablespoons chopped fresh mint
• 1 tablespoon chopped fresh cilantro

• 2 pounds sweet potatoes , peeled and diced
• 3 stalks lemongrass , outer layers removed, bulbs split open
• 2 tablespoons olive oil
• 1 cup minced white onion
• 2 tablespoons minced garlic
• 1 jalapeno pepper , seeded and minced
• 1 piece (2 inches) fresh ginger , peeled and minced
• 1 can (14 ounces) coconut milk
• Juice of 1 lime
• 1 1/2 teaspoons salt
• 1/4 teaspoon cayenne pepper (optional)

To make pesto: Preheat oven to 350°F. Spread peanuts on a small baking sheet and bake until toasted and fragrant, 8 to 10 minutes; cool. Place peanuts on a cutting board and set a heavy saucepan on top. Press down on pan to break peanuts into small, irregular pieces. In a small bowl, combine peanuts with remaining ingredients. Makes 1 1/4 cups.

To make soup: In a large saucepan, combine sweet potatoes and lemongrass with enough cold water to cover; bring to a boil. Reduce heat to medium; simmer until potatoes are tender, about 20 minutes. Remove lemongrass. Drain potatoes; reserve 3 cups cooking liquid.

Meanwhile, in a medium skillet over medium heat, heat olive oil. Add onion; cook, stirring occasionally, until soft, about 5 minutes. Add garlic and cook about 1 minute. Add jalapeño and ginger; cook, stirring, about 2 minutes.

In a blender or food processor, process potatoes, onion mixture, coconut milk and 1 1/2 cups reserved cooking liquid in batches until smooth.

Return soup to same saucepan and stir in remaining 1 1/2 cups reserved cooking liquid; bring to a simmer over medium heat. Stir in lime juice, salt and cayenne pepper. Serve immediately with peanut pesto or cool to room temperature and chill at least 1 hour.