Preheat the oven to 400 F degrees.

Arrange sliced eggplant in a single layer on 2 sheet pans – trim off the eggplant outermost curvy portion so that the slices lay mostly flat. Brush 2 1/2 tablespoons of the oil over both sides of all of the slices. Sprinkle 1/2 teaspoon salt and 1/4 teaspoon pepper over the top.

Roast the eggplant until it is soft and golden, about 25 minutes, flipping the slices over halfway through. Remove from the oven and reduce the temperature to 350 F degrees.

Meanwhile, in a large skillet heat the remaining 1/2 tablespoon oil over medium heat. Add the sliced mushrooms. Sauté until the mushrooms are soft, about 7 minutes.

Add the minced garlic, 1/2 teaspoon salt, and oregano. Cook for another 2 minutes.

Remove the pan from the heat and add the marinara pasta sauce. Stir to combine.

In a large bowl add the ricotta, 1/4 cup parmesan, egg, and remaining 1/2 teaspoon salt and remaining 1/4 teaspoon pepper. Mix well, until the mixture is evenly combined.

Stir in the spinach, using a fork to break it up and distribute it as evenly with the ricotta mixture as possible.

Spoon half of the mushroom marinara sauce on the bottom of the prepared baking dish and spread it into an even layer. Lay 4 eggplant slices on top followed by all of the ricotta mixture. Layer on another 4 slices of eggplant and finish with the remaining mushroom marinara sauce.

Top with the mozzarella and remaining 1/4 cup parmesan. Bake for 25 to 30 minutes, until the cheese is melted and the lasagna is hot and bubbly.

Remove from the oven and sprinkle with fresh herbs.

Let rest 5 to 10 minutes, then serve.