In a large pot, combine the ham hocks, bay leaf, and water together. Season with salt and pepper. Bring the liquid up to a boil and reduce to a simmer. Cook the ham hocks for 30 minutes. With a slotted spoon remove the hocks, remove the meat and chop. Reduce the heat to medium and add the greens, a handful at a time and blanch until they are wilted. Drain and reserve the liquid. Chop the greens. Set aside. In the same pot, heat the oil. When the oil is hot, sauté the vegetables until they are wilted, about 10 minutes. Add the ham hock, greens, reserved liquid, and herbs. Bring to a boil and reduce to a simmer. Cook for 1 1/2 hours. Add the file powder right before serving. Season with salt and pepper. Ladle the gumbo in a shallow bowl and place a spoonful of the rice in the center. Garnish with green onions and Essense.
Yields: 8 servings