Preheat the oven to 400°F (200°C) and prepare baking sheets lined with parchment paper or coated with olive oil.

Wash and slice the eggplants into medium-thick rounds, sprinkle with salt, and let them sit on paper towels for 15 minutes.

Roast the salted eggplant slices in the oven for 20-25 minutes until tender and golden brown.

Heat olive oil in a skillet over medium heat, add diced onions, and sauté until translucent. Stir in minced garlic and sliced mushrooms, and cook until browned.

In a separate bowl, combine ricotta cheese, egg, optional Parmesan, and parsley, mixing until smooth.

Reduce oven temperature to 375°F (190°C).

Spread a thin layer of marinara sauce in a baking dish, layer with roasted eggplant slices, followed by the cheese and mushroom filling.

Repeat the layering with remaining ingredients: eggplant, cheese mixture, mushroom filling, marinara sauce, and mozzarella cheese.

Cover with foil and bake for 30 minutes, then remove foil and bake an additional 10-15 minutes until cheese is bubbly and golden.

Let the lasagna rest for 10 minutes before slicing and serving. Garnish with fresh basil.