In a skillet drizzle in the olive oil and then sauté the sausage, onion, garlic, peppers, and celery together for 5 minutes.
Remove the vegetables from the pan and then add the butter and let it melt. Stir in the flour and keep stirring while you cook it over a medium heat. The mix will turn a beautiful caramel colour. Then you can take it off the heat.
Pour the butter and flour mix into the slow cooker along with the cooked vegetables and sausage, can of tomatoes, chicken stock, creole seasoning, oregano, bay leaves, thyme and Worcestershire sauce. Mix it together.
Add the chicken breasts in and submerge them under the liquid. Then place the lid on and cook on high for 3-4 hours.
Take the chicken breast out of the pot and use two forks to shred, it should pull apart really easily (cook a bit longer if it doesn't). While you do that, pop the shrimp in and give it a stir and cook for another 5 minutes.
Add the shredded chicken back into the pot and mix it all together. Sprinkle the green onions over the top and serve.