In a large Dutch oven set over medium heat, melt the butter. Add the flour and stir continuously to make a roux. Stir the roux over medium heat until the color of peanut butter, 5 to 7 minutes. Add the onions, bell peppers, celery, and garlic to the roux, and cook, stirring often, for 10 minutes. Add the tomatoes to the pot and season with the bay leaves, salt, cayenne, and 1 tablespoon Essence. Cook the tomatoes for 2 to 3 minutes and then whisk in the Shrimp Stock.

Bring the pot to a boil, and reduce to a simmer. Cook the etouffée, stirring occasionally, for 45 minutes. Season the shrimp with the remaining tablespoon Essence and add them to the pot, stirring to evenly distribute. Cook the shrimp for 5 to 7 minutes, or until they are cooked through. Add the chopped parsley to the pot and stir to combine. Serve the etouffée with steamed white rice. Garnish with the green onion tops.