01 - Preheat oven to 400°F. Line two baking sheets with parchment paper.
02 - Arrange eggplant slices on baking sheets. Brush both sides with olive oil and season with salt and pepper. Roast for 20 minutes, flipping halfway, until softened and lightly golden. Remove from oven and reduce heat to 375°F.
03 - In a bowl, mix ricotta, Parmesan, egg, basil, nutmeg, salt, and pepper until smooth and well combined.
04 - Spread 1/2 cup marinara sauce on the bottom of a 9x13-inch baking dish. Layer half of the roasted eggplant slices over the sauce.
05 - Spread half of the ricotta mixture over the eggplant, then top with 1 cup marinara sauce and 1 cup mozzarella cheese.
06 - Repeat layers with remaining eggplant, ricotta mixture, marinara sauce, and mozzarella cheese.
07 - Sprinkle the top with remaining 2 tbsp Parmesan. Cover with foil and bake for 25 minutes. Remove foil and bake an additional 15-20 minutes until bubbly and golden on top.
08 - Let casserole rest for 10 minutes before garnishing with fresh basil leaves and serving.