Preheat the oven to 350°F.
Slice the eggplant into 1/4-inch-thick rounds.
In a shallow dish whisk together 1 large egg, 1/4 cup milk, and 1/8 teaspoon ground black pepper.
In another shallow bowl stir together 1 cup panko, 1 ounce Parmesan cheese, and 1 tablespoon dried basil.
Working one slice at a time, dip an eggplant slice into the egg mixture to coat, let excess drip off, then press both sides into the panko mixture so the crumbs adhere. Repeat for all slices.
Spray a 9×13-inch baking dish with the nonstick cooking spray from the ingredient list and arrange the coated eggplant slices in the dish in a single layer (they may overlap slightly).
Pour 1 1/2 cups spaghetti or marinara sauce evenly over the arranged eggplant.
Bake uncovered in the preheated oven for 40 minutes, or until the eggplant is tender when pierced with a fork.
Remove the dish from the oven, sprinkle 3 ounces mozzarella cheese evenly over the top, then return to the oven and bake uncovered 10 minutes more, or until the cheese is melted and lightly browned.
Let the dish rest a few minutes before serving.