Cut the corn kernels from the cobs, then, using the back of the knife, scrape the cobs to release the corn milk. Set aside.
Put the scraped cobs in a large, heavy pot or Dutch oven. Add the ham bone and water and bring to a boil. Reduce the heat to medium low and simmer for about 1 1/2 hours. Remove the cobs and discard. Remove ham bone and discard.
Heat the oil in a large skillet and saute the sausage until golden brown, stirring frequently, about 6 minutes. Add the onions and celery to the hot skillet and cook, stirring, until the vegetables are soft and light golden brown, about 8 minutes. Add the tomatoes and cook until they begin to break down, about 2 minutes. Transfer the sausage-vegetable mixture to the pot with the corn broth along with the corn kernels, Essence, salt, thyme bundle, and bay leaf, and simmer for 30 minutes. Remove the thyme bundle and bay leaf, add the green onions and parsley and serve.
Yield: 2 1/2 quarts, 8 servings