Prepare the Grill: Preheat an outdoor grill before beginning the eggplant preparation.
Slice the Eggplant: Cut the eggplant into rounds, keeping the slices suitable for layering inside the sandwiches.
Season the Eggplant: Place the eggplant rounds in a bowl and toss them with olive oil, salt, and pepper so they are evenly coated.
Grill the Eggplant: Place the seasoned eggplant rounds on the preheated outdoor grill and cook until tender and grilled.
Build the Sandwiches: Layer the grilled eggplant onto the bread, then add marinara sauce, provolone cheese, and Parmesan cheese to create the filling.
Coat the Bread: Spread butter or olive oil over the outside surfaces of the bread slices to help them become golden during cooking.
Press the Sandwiches: Place the assembled sandwiches in a panini press or cook them in a skillet until the cheese has melted and the bread is golden brown.
Serve the Sandwiches: Remove the sandwiches once the bread is crisp and golden and the cheese is fully melted, then serve warm.