Preheat your oven to 375°F (190°C) and lightly grease a 9×13-inch baking dish.

Cook lasagna noodles in boiling water until al dente, about 8-10 minutes, then drain and lay flat to cool.

In a skillet, sauté chopped onion in olive oil until translucent, add minced garlic and sliced mushrooms, cooking for 5-7 minutes until golden, then stir in spinach and season with salt and pepper before cooling.

In a mixing bowl, combine ricotta cheese, half of mozzarella, Parmesan, and the cooled mushroom-spinach mixture, then add the egg and mix until well blended.

Spread 2-3 tablespoons of the filling on each noodle, roll tightly and place seam-side down in the baking dish.

Pour marinara sauce over the rolls and sprinkle with remaining mozzarella and optional extra Parmesan.

Cover tightly with foil and bake for 25-30 minutes; then uncover and bake for an additional 5 minutes to brown the cheese.

Let the rolls rest for about 5 minutes before serving, and garnish with fresh basil and grated Parmesan.