Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper.
Slice the eggplants into ½-inch thick rounds and place them on the prepared baking sheet.
Drizzle the olive oil over the eggplant slices and sprinkle with salt and pepper. Toss gently to coat.
Bake in the preheated oven for 20 minutes, flipping the slices halfway through, until they are tender and lightly browned.
While the eggplants are baking, prepare the ricotta mixture. In a mixing bowl, combine the ricotta cheese, grated Parmesan cheese, dried oregano, and a pinch of salt and pepper.
Remove the eggplant slices from the oven. Spread a spoonful of marinara sauce on each slice, followed by a dollop of the ricotta mixture.
Sprinkle shredded mozzarella cheese over the top of each slice.
Return the eggplants to the oven and bake for an additional 10 minutes, or until the cheese is melted and bubbly.
Let cool for a few minutes before serving. Garnish with fresh basil leaves if desired.