Place the meat, if using, with the salt, cayenne, and bay leaves in a large deep pot and add water. Bring to a boil over medium-high heat and cook for 30 minutes. If using meat, remove it with a slotted spoon, chop it, and set aside.
Reduce the heat to medium and add the greens, a handful at a time, and blanch until they are wilted, about 5 minutes. Drain, reserving the liquid. Coarsely chop the greens. Set aside.
In the same pot, heat the oil over medium heat and add the onions, bell peppers, and celery. Cook, stirring often, until the vegetables are wilted and golden, about 10 minutes.
Add the meat, greens, reserved liquid, thyme, oregano, basil, and parsley. Bring to a boil, reduce heat to medium-low, cover, and simmer for 1 1/2 hours. Remove the bay leaves. Adjust seasonings with salt, if desired. (If not using meat, the gumbo may need more salt.) Also, if no meat has been added, add 4 tablespoons butter to the pot just before removing from the heat.
Serve in deep soup bowls over steamed white rice with file powder passed at the table for guests to thicken the gumbo to their personal taste. Serve with hot sauce, if desired.
Recipe courtesy of Louisiana Real and Rustic, by Emeril Lagasse and Marcelle Bienvenu, William and Morrow Publishers, 1996