Add the beans to a large bowl. Rinse them, then cover with cool water and allow to soak for 6 hours or overnight.
Add the olive oil to a soup pot over medium heat.
Once the oil is hot, add the celery, onion, green pepper and mushrooms. Cook for about 7 minutes until softened.
Add the garlic and cook 1 minute more, stirring constantly.
Add the soaked beans, broth, bacon bits, bay leaf, thyme, cajun seasoning and salt. Stir well. Bring to a simmer then lower the heat to medium low, cover and cook for 30-60 minutes, until the beans are tender. Remove the lid and cook for an additional 30 minutes to reduce the liquid.
Remove the bay leaf. Serve over rice and garnish with green onions.