In a saucepan, combine the chipotles, onion, tomatoes, carrots, celery, cilantro, broth, and salt and pepper and cook, uncovered, over medium heat for 10 minutes. Reduce the heat to simmer and cook for 30 minutes.
While the sauce is cooking, combine the remaining ingredients in a bowl, mix well, and fashion into meat balls. Bake the meatballs in the oven for 20 minutes at 350 degrees F. Remove, drain, and add them to the chipotle sauce. Simmer in the sauce for 20 minutes, and serve.
