Preheat the oven to 350°F. Lightly grease a 9- by 13- inch casserole dish with 2 teaspoons of the butter and set aside.
Heat at least 4 inches of oil in a large saucepan or deep fryer to 360°F.
Separate the onion slices into individual rings. Combine with the Crystal Hot Sauce in a mixing bowl and toss thoroughly. Place 2 cups of the flour in a large mixing bowl and, working in batches, dredge the onion rings in the flour to coat. Transfer the coated onion rings to a colander or strainer and shake over the mixing bowl containing the flour to release any loose flour from the prepared rings. Fry the onion rings in batches until just lightly golden, about 1 minute per batch. Note: it is important to allow the temperature to return to 360°F between batches. As batches are completed, transfer the onion rings to paper-lined baking dish to drain. Season the onion rings with the Essence and set aside. Repeat with the remaining batches.
Melt the remaining 6 tablespoons of butter in a large saucepan over high heat and sauté onion and celery until soft, about 6 minutes. Add the garlic and cook, stirring, for 1 minute. Add the mushrooms, Bayou Blast and salt and cook, stirring frequently, until mushrooms are soft and golden brown and have released their liquid, 4 to 6 minutes. Sprinkle with the remaining ¼ cup of flour and stir to combine. Cook for 2 minutes, stirring constantly. Add the chicken broth and heavy cream and continue to cook, stirring frequently, until sauce is thick and creamy and any floury taste is gone, about 15 minutes. Remove from the heat.
In a large bowl combine the green beans, mushroom sauce, and cubed fontina cheese. Transfer to the prepared casserole dish and top with the fried onion rings. Bake for 20 to 25 minutes, or until the casserole is hot and bubbly and onion rings are golden brown. Serve immediately.
Yield: 8 to 10 servings