- 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 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.