Heat oil in a large saucepan over medium heat, stir in onion, carrots and ginger; cook for 2 to 3 minutes or until softened.
Stir in pumpkin, chicken broth, coconut milk, sugar and cinnamon. Bring to a boil, remove from heat and stir in sour cream and lime juice. (If using fresh cubed pumpkin, boil until softened; 10 to 15 minutes.)
Puree soup until very smooth in an electric blender or using a stick blender. Garnish with a swirl of sour cream and sprinkle of cinnamon, if desired. Serve immediately.
Serving Suggestion: This soup is delicious served with traditional Tostonés as a garnish or accompaniment.