Melt butter in a large stock pot over medium-high heat.
Whisk in flour a little at a time until there are no lumps and a thick and creamy roux begins to form. Cook the roux until it turns a light brown color, like the color of caramel. Stir constantly! Be patient and don’t let the roux burn. If you burn the roux, you must start over again.
After roux is cooked, add the onions, peppers and celery. Cook for about 6 minutes.
Add the garlic and cook for another 2 minutes.
In a slow, steady stream, whisk in the chicken stock. Whisk constantly to prevent lumps.
Add sausage and chicken to pan.
Add the diced tomatoes, crab legs (if using), Worcestershire sauce, cayenne, paprika, oregano, hot sauce, thyme, bay leaves, and salt and pepper.
Bring gumbo to a boil, uncovered, and then lower the heat to medium low and simmer for an hour.
Remove the chicken thighs and set aside to cool.
Add okra and simmer for another hour.
Shred the chicken meat. Discard the bones.
During the last 15 minutes of cooking, add the shredded chicken meat, shrimp, oysters, crab meat and parsley.
Remove two bay leaves and crab legs before serving.
Serve gumbo over hot, cooked rice. Garnish with green onions