Adapted from Martha Hall Foose's recipe in Screen Doors and Sweet Tea, this soup makes the most of a trip to the farmer's market.
• 3 pounds sweet potatoes, peeled and diced
• 3 tablespoons unsalted butter
• 3 leeks, white and tender parts only, sliced
• 1 tablespoon peeled, diced ginger
• 2 2-inch pieces lemongrass
• 2 garlic cloves, minced
• 1 tablespoon curry powder
• 1 quart vegetable broth
• 1 fourteen-and-a-half-ounce can coconut milk
In a large pot, melt butter, then cook sweet potatoes for five minutes over medium heat. Add leeks, ginger, and lemongrass. Cook over low heat until leeks are tender—about three minutes. Add garlic and curry and cook for one minute. Stir in broth and simmer until potatoes are very tender—about 20 minutes.
Using an immersion blender, conventional blender, or food processor, puree soup until very smooth. Return to pot and whisk in coconut milk. Warm through over very low heat.