To prepare the shrimp: In a 6-quart saucepan set over high heat, combine the water with 2 teaspoons of the crab boil, the lemons, the bay leaves, and a generous amount of salt (enough to make it taste almost like sea water), and bring to a boil.

Prepare an ice bath, and add the remaining 1 teaspoon crab boil to it along with enough salt to make the water taste like the sea.

Add the shrimp to the boiling water and cook for 2 to 3 minutes, or until just cooked through. Immediately transfer the shrimp to the ice bath and allow them to cool. As soon as the shrimp are cool enough to handle, chop them into bite-size pieces. Toss the shrimp with enough of the Rémoulade Sauce to coat (about 1/4 cup), and refrigerate until you are ready to assemble the sandwiches. (Reserve the remaining Rémoulade Sauce.)

To fry the tomatoes: Slice the tomatoes crosswise into 1/4-inch-thick slices. Season the tomatoes with 1/2 teaspoon of the salt and 1/4 teaspoon of the pepper. Put the flour in a shallow bowl and season it with the remaining 1/2 teaspoon salt, 1/4 teaspoon pepper, and the cayenne. In another shallow bowl, whisk together the buttermilk and eggs. Put the cornmeal in another shallow bowl. Dredge the tomatoes first in the flour, coating the slices evenly on both sides and tapping off any excess. Dip them in the egg wash and let the excess drip off. Then dredge them in the cornmeal, tapping off any excess. Set aside on a plate.

Heat the 1/2 cup vegetable oil in a large sauté pan over medium heat. Pan-fry several tomato slices in the hot oil until golden brown, about 2 minutes on each side. Drain on paper towels. Add more oil to the pan as necessary to fry the remaining tomato slices.

To assemble the sandwiches: In a small bowl, toss the chopped romaine with the extra-virgin olive oil.

Lay 4 slices of the toast on a work surface, and top each one with 1 tablespoon of the remaining Rémoulade Sauce. Evenly divide the lettuce among them, top with the fried green tomato slices, and add the bacon. Place 1/2 cup of the shrimp on top of the bacon, and then top each with a remaining slice of toast. Cut the sandwiches in half and serve immediately.