Heat oil (or oil/butter) in large saucepan over medium heat. Add ginger and onion and cook, stirring occasionally, until soft and fragrant, about 5 minutes.

Add carrots, broth and juice. Raise the heat to medium high and bring to a boil. Reduce heat to low, cover and simmer until carrots are very tender, about 45 minutes.

Puree the soup in the saucepan using an immersion blender, or let soup cool a bit and puree in blender or food processor and return to the saucepan. Add nutmeg, salt and pepper to taste. Add heavy cream just before serving.