- With the rack in the middle position, preheat the oven to 200°C (400°F). Oil a 20-cm (8-inch) square Pyrex baking dish.
- Pour the beaten eggs into the dish. Season with salt and pepper. Bake until firm, about 10 minutes. Cut the omelet into quarters. Using a spatula, lift the pieces from the dish. Keep warm.
- Meanwhile, dredge the eggplant slices in the flour. In a large skillet over medium-high heat, brown on both sides in the oil. Set aside.
- Toast 3 slices of bread for each sandwich. Spread a generous amount of hummus on 1 slice. Top with 1 piece of omelet and 1 eggplant slice. Top with another slice of bread. Spread with mustard to taste. Top with 2 tomato slices and 1 piece of lettuce and finish with 1 slice of bread spread generously on the underside with hummus. Secure with 4 toothpicks and cut into quarters.
- Serve immediately.
Prepare just before serving.