Put 1/2 pound of the crawfish in a food processor and pulse 2 to 3 times to chop coarsely. Add 2 tablespoons of the shallots, 1/2 cup of the green onions, 2 teaspoons of the garlic, and the celery, and pulse several times to mix well. Add the mustard, mayonnaise, lemon juice, coriander, crab boil, and hot sauce, pulse several times to mix, and season with salt and pepper.
Melt the butter in a large sauté pan over medium heat. Add the remaining 2 tablespoons of shallots and the chopped morels. Cook, stirring, for 1 minute, and season with salt and pepper. Add the remaining 2 teaspoons garlic, the remaining 1/2 pound crawfish tails, and the remaining 1/4 cup green onions. Season with Essence and cook, stirring, for 2 minutes. Remove from the heat and stir in the bread crumbs. Let cool completely.
Make a small slit on 1 side of each of the whole morels. Stuff each with about 2 teaspoons of the stuffing. Press to close.
In a small mixing bowl, combine the flour and cornstarch and season with Essence. Whisk to blend. In a medium-size mixing bowl, whisk the egg and soda water together to blend. Add the flour mixture to the egg mixture and whisk until smooth.
In a large, deep, heavy pot or electric fryer, heat 4 inches of vegetable oil to 360ºF.
Dip the stuffed morels, 3 or 4 at a time, in the batter, letting the excess drip off. Fry in batches in the hot oil for 2 to 3 minutes, stirring constantly to brown evenly. Drain on paper towels.
Sprinkle with Essence and serve the morels with the crawfish sauce on the side.
Yield: 4 servings