In a large pot, preheat olive oil over medium heat. Sauté onions, yams and sweet potatoes 5-7 minutes or until edges start to brown. Pour in chicken broth and all spices. Cover and bring to boil. Reduce heat and simmer 30 minutes or until veggies are fork tender. Remove bay leaf and blend soup until completely smooth. Place pureed soup over low heat and stir in coconut milk.
When ready to serve, ladle into bowls and top with marshmallows.