Gather the ingredients.

Clean chitterlings by removing all specks and any pieces of fat with specks on them. Rinse in several changes of salted water.

Place cleaned chitterlings into a large pot and fill with enough water to cover; bring to a boil over medium-high heat. Drain, rinse, and return to the pot. Fill again with enough water to cover.

Add whole onions, potato, and celery stalks, plus chopped bell pepper, vinegar, garlic, salt, bay leaf, Creole seasoning, and red pepper flakes to the pot. Bring to a boil over medium-high heat, then cover and simmer over medium heat for 3 to 4 hours; chitterlings should appear clear to white in color.

Use a slotted spoon to transfer chitterlings to a cutting board. Cut into 1-inch pieces. Discard onions, potato, celery, and bay leaf. Pour out most of the cooking liquid, then return chitterlings to the pot.