01 - Preheat the oven to 400°F. Line two baking sheets with parchment paper. Arrange the eggplant planks evenly and brush both sides with olive oil. Season lightly with kosher salt and black pepper.
02 - Bake eggplant slices for 15 to 20 minutes, turning halfway through, until tender and flexible but not browned. Remove from oven and set aside to cool slightly. Reduce oven temperature to 375°F.
03 - In a skillet over medium heat, add olive oil and sauté minced garlic for 30 seconds until fragrant. Add chopped spinach and cook until wilted. Transfer mixture to a bowl to cool.
04 - In a large mixing bowl, combine ricotta, grated Parmesan, half the shredded mozzarella, cooled spinach mixture, beaten egg, ground nutmeg, Italian herbs, black pepper, kosher salt, and sliced basil. Stir until thoroughly blended.
05 - Spread 1 cup of marinara sauce evenly over the bottom of a 9x13-inch baking dish. Place 2 to 3 tablespoons of ricotta mixture at one end of each eggplant plank, roll up tightly, and arrange them seam-side down in the prepared dish.
06 - Pour the remaining marinara sauce evenly over the eggplant rolls. Sprinkle with the remaining mozzarella cheese.
07 - Bake uncovered at 375°F for 25 minutes, or until the cheese is bubbling and golden. Rest for 5 to 10 minutes. Garnish with additional fresh basil before serving.