1In a large pot add chicken broth over medium heat; add celery, carrots, onion and green pepper. Cook and stir until carrots are tender; this should be at the boiling point.
2Add pasta, salt and pepper; cook 4 minutes then remove from heat. Place lid on the pot and let it stand 10 minute; or until pasta is done.
3In a saucepan over low heat add butter and melt. Add flour; stir until smooth. Add milk in slowly; stir. Add mustard and stir. Add cheese; stir and cook until cheese is melted and smooth. Remove from heat and add to pasta mixture; stir. Serve when heated through.