Preheat your oven to 400°F (200°C). Slice the eggplant into ¼-inch thick rounds and sprinkle with salt. Let them sit for about 15 minutes.

Arrange the eggplant slices on a baking sheet and drizzle with olive oil. Roast for 20-25 minutes until golden.

In a skillet, heat olive oil over medium heat. Sauté onions until translucent, then add garlic and mushrooms, seasoning with oregano and basil. Cook until the mushrooms are tender.

In a mixing bowl, combine ricotta cheese, optional egg, Parmesan, and parsley until creamy. Set aside.

Spread marinara sauce in a baking dish. Layer roasted eggplant, ricotta mixture, mushroom filling, and mozzarella. Repeat layers and finish with marinara and mozzarella.

Cover with foil and bake at 375°F (190°C) for 30 minutes. Remove foil and bake for an additional 10-15 minutes until bubbling. Let rest for 10 minutes before serving.

Garnish with fresh basil before slicing and serve warm with a salad or garlic bread.