Sauté ginger and garlic in hot oil in a Dutch oven until tender. Add chicken broth and sweet potato; bring to a boil. Reduce heat, and simmer, stirring occasionally, 20 minutes or until potato is tender.
Add coconut milk and next 3 ingredients; cook, stirring occasionally, until thoroughly heated (do not boil). Remove from heat; add green onions and chopped cilantro. Garnish, if desired.
*If you can't find curry oil, substitute sesame oil and add 1/2 teaspoon curry powder.