Preheat your oven to 375°F (190°C) and grease a 9x13-inch baking dish with olive oil or non-stick spray.

Bring a large pot of salted water to a boil, add lasagna noodles, and cook until al dente, about 8–10 minutes. Drain and rinse under cold water.

In a large skillet, heat 2 tablespoons of olive oil. Sauté diced onion until translucent, about 3–4 minutes. Add minced garlic and sliced mushrooms, cooking until tender, around 5–7 minutes. Add spinach and thyme and cook until spinach wilts. Season with salt and pepper.

Spread a thin layer of marinara sauce in the prepared baking dish. Layer three cooked lasagna noodles, half of the ricotta, half of the sautéed mixture, and a third of the mozzarella and Parmesan. Repeat layers, finishing with marinara sauce and remaining cheeses.

Cover with foil and bake for 25 minutes. Remove foil and bake for another 10-15 minutes until cheese is golden brown.

Allow to cool for about 10 minutes before slicing. Garnish with fresh basil and enjoy.