Preheat the oven to 400 degrees F. In a large skillet, over medium heat, add the oil. Add the onions, peppers, and celery. Season with salt and cayenne. Saute for about 5 minute, or until wilted. Add the crawfish tails and cook for about 5 minutes. Remove from the heat and cool completely. In a mixing bowl, combine the crawfish mixture with the garlic, parsley, green onions, 3/4 cup mayonnaise, mustard and hot pepper sauce. Mix well. Spoon the mixture into 4 individual gratin dishes. Mix together the bread crumbs and remaining mayonnaise. Season with Essence. Mix well. Spread the top of the crawfish mixture with the bread crumb mixture. Bake for about 20 minutes, or until bubbly and brown. Remove from the oven and let stand for 2 to 3 minutes before serving.
Emeril's ESSENCE Creole Seasoning (also referred to as Bayou Blast):