Using a food processor, pulse the sour cream and 1/4 cup cilantro until smooth; refrigerate.
In a large saucepan, heat the olive oil over medium-high heat. Add the onion and chipotle chile and cook until softened, about 5 minutes. Add the chicken broth and tomatoes and bring to a boil for 5 minutes. Add the couscous and cook until al dente, about 8 minutes. Stir in the ham; season with salt and pepper.
To serve, top the soup with the cilantro sour cream and remaining 1/4 cup cilantro.