Creating Chicken, Mushroom, and Spinach Lasagna is straightforward if you follow these steps:

1. Preheat the Oven: Preheat your oven to 375°F (190°C).
2. Cook the Lasagna Noodles: In a large pot of boiling salted water, cook the lasagna noodles according to the package instructions. Drain and set aside.
3. Sauté the Vegetables: In a large skillet, heat olive oil over medium heat. Add the chopped onion and sauté for 2-3 minutes until softened. Add minced garlic and diced mushrooms. Cook for another 4-5 minutes until mushrooms are tender.
4. Combine Chicken and Spinach: Stir in the shredded chicken and chopped spinach. Cook until the spinach wilts. Season with Italian seasoning, salt, and pepper. Remove from heat.
5. Mix the Cheese Filling: In a bowl, combine the ricotta cheese, 1 cup of mozzarella, and half of the grated Parmesan cheese. Mix well.
6. Layer the Lasagna: In a 9×13 inch baking dish, spread a thin layer of marinara sauce on the bottom. Place three lasagna noodles over the sauce. Spread half of the ricotta cheese mixture over the noodles.
7. Add Mushroom and Chicken Mix: Layer half of the chicken, spinach, and mushroom mixture over the ricotta. Add another layer of marinara sauce.
8. Repeat the Layers: Repeat the layering process, starting with noodles, ricotta, chicken mixture, and marinara until all ingredients are used, finishing with noodles and marinara sauce on top.
9. Add Toppings: Sprinkle the remaining mozzarella and Parmesan cheese on top of the last layer.
10. Bake the Lasagna: Cover the dish with aluminum foil and bake for 25 minutes. Remove the foil and bake for an additional 20-25 minutes or until cheese is bubbly and golden.
11. Cool and Garnish: Remove from the oven and let it cool for about 10-15 minutes. Garnish with fresh basil before serving.

These straightforward steps will guide you in creating an incredible Chicken, Mushroom, and Spinach Lasagna with ease.