Heat the oil in a 10-inch skillet over medium-high heat. Add the onions and cook until they begin to brown, stirring occasionally. Reduce the heat to medium. Cook until the onions are tender and caramelized, stirring occasionally. Remove the skillet from the heat.
Heat the broth, black pepper, carrots and celery in a 4-quart saucepan over medium-high heat to a boil. Stir the campanelle and chicken in the saucepan. Reduce the heat to medium. Cook for 10 minutes or until the campanelle is tender. Stir in the onions and serve immediately.