Heat oil in a large saucepan over medium heat. Add onion, cover and cook, stirring occasionally, until browned, 4 to 5 minutes. Add cumin and cook, stirring, until fragrant, about 30 seconds. Add beans, water, orange zest and juice, salt and pepper; increase heat to medium-high and bring to a boil, stirring often. Transfer to a blender with cilantro, lime juice and 3 tablespoons sour cream. Puree until smooth. (Use caution when pureeing hot liquids; see Tip.)
Combine the remaining 1 tablespoon sour cream and ground chipotle in a small bowl. Serve the soup garnished with the chipotle cream and scallions.
Hot liquids can splatter out of a blender when it¿s turned on. To avoid this, remove the center piece of the lid. Loosely cover the hole with a folded kitchen towel and turn the blender on. Better airflow will keep the contents from spewing all over the kitchen¿and yourself. Ingredient Note: Chipotle peppers are dried, smoked jalapeno peppers. Ground chipotle can be found in the specialty spice section of most supermarkets.