In a large pot, heat the 2 tablespoons of vegetable oil. Season the duck pieces with Rustic Rub. When the oil is hot, sear the duck pieces for 2 minutes on each side. Remove the duck from the oil and set aside. Combine the remaining oil and flour in the pot. Continue to cook, stirring the mixture constantly for 12 to 15 minutes, until a medium brown roux is formed; the roux should be the color of peanut butter. Add the onions, bell peppers, celery, and duck pieces. Reduce the heat to a simmer and cook for 10 minutes. Add the mushrooms and garlic. Season with salt and cayenne. Add the thyme and bay leaves. Cook the mixture, stirring often, for 5 minutes. Add the stock and water. Bring the mixture up to a boil and reduce to a simmer. Cook for 2 hours, skimming any fat that may rise to the surface. Taste and adjust the seasoning if necessary. Serve the gumbo in shallow bowls and garnish with the rice and green onions. Serve with crusty bread.
Combine all ingredients and store in an air-tight container.