In large saucepan, heat oil over medium heat; cook onion, garlic, ginger, cumin, coriander, turmeric and red pepper flakes, stirring until onion is softened, about 3 minutes.
Add broth, sweet potatoes and coconut milk; bring to boil.
Cover and reduce heat to low; cook for 12 to 15 minutes or until potatoes are tender.
Let cool slightly. Purée in batches in blender or food processor or with hand held blender until smooth.
Return to saucepan. Stir in lime juice. Season to taste with salt.
Serve garnished as desired.
