Season the shrimp with salt and black pepper. Combine the water, liquid crab boil, lemon, and bay leaves in a large, heavy pot. Season the mixture with more salt and black pepper. Bring the mixture to a boil, add the shrimp and cook for 1 minute. Remove from the heat and let sit for 1 minute. Drain and discard the liquid. Let the shrimp cool to room temperature, then refrigerate for about 2 hours.
Combine the egg, lemon juice, onions, green onions, celery, horseradish, mustards, ketchup and parsley in a food processor. Process until the mixture is smooth. Season to taste with salt, black pepper and cayenne. While the machine is running, slowly add the olive oil, a little at a time, until the mixture is thick and smooth. Reseason if needed. Refrigerate the mixture for 2 hours.
Season both sides of the sliced tomatoes with salt and black pepper. Put the flour, egg wash, and breadcrumbs in 3 separate shallow dishes and season with the Essence. Dredge each tomato slice first in the flour, then in the egg wash, letting any excess drip off, then dredge in the breadcrumbs, coating evenly.
Heat 1/4 cup of the vegetable oil in each of two skillets over medium-hot heat. Fry the tomatoes until crispy, about 2 minutes on each side. Drain on paper towels and season with salt and black pepper.
To serve, combine the shrimp and dressing mixture in a bowl and mix well. Arrange 3 tomatoes on the rim of 4 salad plates. Spoon equal amounts of the rock shrimp mixture in the center of each plate. Garnish with the maiche if you wish.
Makes 4 servings