Preheat broiler to high.
Set up dredging station: Place flour in a shallow dish. Place eggs in another dish and the panko in another. Sprinkle each eggplant slice evenly with salt on both sides. Dredge both sides of the eggplant slices in the flour; then the egg, and lastly in the panko. Place the breaded eggplant slices on a baking sheet lightly coated with cooking spray or on a prepared non-stick baking sheet. Broil the eggplant for 3 minutes on each side or until lightly browned. Transfer eggplant slices to a plate.
Place marinara in a microwave-safe bowl and microwave on HIGH for 2 minutes or until hot; keep warm.
Place your toasted bread slices on the baking sheet; lightly drizzle a little olive oil on each toast and top each slice with a little of the marinara sauce. Place 1 eggplant slice on each toast and then top the eggplant with 1 basil leaf, a slice of mozzarella cheese, a couple tomato slices and then finish with the remaining slice of eggplant (you'll have 2 slices of eggplant per sandwich).
Broil the eggplant stacks for about 3 minutes or until cheese is lightly browned, melting and bubbly. Spoon some marinara over each serving. Top with remaining torn basil leaves and season with freshly ground black pepper. Serve immediately.