Peel and thinly slice the carrots. Finely chop the onion. Peel and chop the garlic cloves. In a large saucepan, heat oil over medium heat. Add carrots, onion, garlic, and ginger and cook, stirring occasionally, until onion is golden, 6 to 8 minutes. Meanwhile grate the orange to yield 2 teaspoon grated zest. Juice orange to yield 1/2 cup orange juice.
Add chicken stock, orange zest, and bay leaf to cooking vegetables. Bring to a boil. Reduce heat to medium-low, cover and cook, stirring occasionally, until carrots are tender about 20 minutes.
In a food processor or blender, puree soup in batches until smooth; return to saucepan. Stir in orange juice and season with salt and pepper to taste. Cook over medium heat, stirring occasionally, until heated through, 2 to 3 minutes. Mince cilantro or parsley to yield 2 tablespoons. Garnish each soup bowl with a dollop of sour cream or yogurt and sprinkling of cilantro and serve.