1. Preheat oven to 375°F (190°C).
2. Cook the lasagna noodles according to package instructions. Drain and set aside.
3. In a skillet, heat olive oil over medium heat. Add minced garlic and sauté until fragrant.
4. Add sliced mushrooms and cook until tender. Add spinach and cook until wilted. Season with salt and pepper. Remove from heat.
5. In a baking dish, spread a thin layer of marinara sauce. Place a layer of lasagna noodles on top.
6. Spread a layer of the mushroom-spinach mixture over the noodles. Add dollops of ricotta cheese, then sprinkle with mozzarella and Parmesan cheese.
7. Repeat layers until all ingredients are used, ending with a layer of cheese on top.
8. Cover with aluminum foil and bake for 20 minutes. Remove foil and bake for an additional 20 minutes, or until cheese is bubbly and golden.
9. Let lasagna rest for 10 minutes before serving.