In a heavy stock pot, combine chicken, onions, celery stalk, garlic and broth (enough to cover your chicken, use water if the can of broth isn't enough). Cover and cook @ 300 degrees for 1 1/2 hours.
Remove the chicken from pot, reserve 1/2 cup broth and discard the rest. Shred the chicken with two forks, return to the pot with the 1/2 cup broth and the hot sauce (use more hot sauce if you really like to spice things up). Mix well.
To prepare lettuce cups, place 1/2 cup buffalo chicken in each leaf, top with 1/4 cup shredded carrots, celery and dressing of your choice. Wrap up and start eating!