Preheat oven to 400°F. Line a large rimmed sheet pan with parchment paper and lightly spray with cooking spray.
Lay eggplant slices on paper towels. Sprinkle with salt on both sides and let sit for 10 minutes to draw out moisture. Pat completely dry.
Set up breading station: beaten egg in one shallow bowl, breadcrumbs seasoned with salt and pepper in another.
Dip each eggplant slice in egg, letting excess drip off. Coat thoroughly in breadcrumbs, pressing gently so crumbs adhere.
Arrange breaded eggplant in a single layer on prepared sheet pan. Spray tops generously with cooking spray or drizzle lightly with olive oil.
Bake for 12-15 minutes until bottoms are golden and crispy.
Remove from oven and flip each slice. Top each with a spoonful of marinara sauce and a generous amount of shredded mozzarella.
Return to oven and bake another 8-10 minutes until cheese is melted, bubbly, and beginning to brown.
Remove from oven and garnish with fresh basil and grated Parmesan if desired. Serve immediately.