Heat the oil in a large saucepan. Add the onion and cook over moderately low heat, stirring occasionally, until softened, about 5 minutes. Add the carrots and ginger and cook for 5 minutes, stirring occasionally. Add 2 cups of the stock, season with salt and pepper and bring to a boil. Cover and simmer over low heat until the carrots are tender, about 25 minutes.
2. Strain the cooking liquid into a heatproof bowl. Discard the ginger. In a blender, puree the vegetables with 1 cup of the cooking liquid until smooth. Stir the puree into the cooking liquid in the bowl and add the lemon juice, honey and remaining 1/2 cup of stock. Refrigerate until chilled or for up to 1 day. Season the soup with salt, pepper and hot sauce and serve garnished with cilantro leaves.