Rinse and sort beans.
To a large heavy pot over medium heat, add oil.
Add sliced sausage to pot, and sauté for 5 minutes.
Put the onions, bell pepper, celery, and garlic into pot, and sauté till soft and translucent.
Add beans, water, cayenne, and bay leaf to pot.
Bring it all to a boil, reduce heat, and simmer uncovered for 1-2 hours, or until beans are tender. Add additional water as necessary. Don't let it dry out and burn.
For a creamier consistency, mash some beans against the side of the pot or use a stick blender.
Add salt, pepper, and creole seasoning to taste.
Just before serving, stir in fresh parsley and green onions, and serve with hot cooked rice.