In a large saucepan or kettle cook pancetta or bacon (if using) just until crisp. Add ground beef; cook until meat is no longer pink. Drain well.
If desired, pass undrained tomatoes through a food mill or sieve. Or, process in blender or food processor until nearly smooth. For sauce, add the tomatoes, onion, lentils, carrot, celery, parsley, tomato paste, and bouillon granules to meat. Stir in the water and wine or broth. Bring to boiling; reduce heat. Cover and simmer about 40 minutes or until lentils are tender, stirring occasionally. Uncover and simmer about 5 minutes more or until of desired consistency.
Meanwhile, cook pasta according to package directions. Drain well.
Stir evaporated milk into meat mixture; heat through. Serve sauce over pasta. If desired, top with Parmesan cheese and garnish with celery leaves. Makes 6 servings.