Heat the oil in a large, heavy bottomed pot over medium heat. Add the onion and ginger and cook, stirring occasionally, until the onion is translucent, about 5 minutes. Add the carrots, salt, and pepper and stir to coat. Add the vegetable broth and bring to a boil. Reduce the heat, cover, and simmer until the carrots are tender, about 20 minutes. Puree the soup with an immersion blender (or in batches in a regular blender). Stir in the orange juice, coconut milk, and cinnamon. Serve garnished with the mint, if using.