Step-by-Step Instructions

1. Preheat the Oven:
   • Preheat your oven to 375°F (190°C).
2. Cook the Lasagna Noodles:
   • In a large pot, bring salted water to a boil. Cook the lasagna noodles according to the package instructions until al dente. Drain and set aside.
3. Sauté the Mushrooms and Spinach:
   • In a skillet, sauté the sliced mushrooms over medium heat until they release their moisture and become tender, about 5-7 minutes.
   • Add the spinach to the skillet and cook until wilted. Remove from heat and set aside.
4. Prepare the Chicken:
   • If not using pre-cooked chicken, cook the chicken in the same skillet until fully cooked and no longer pink. Shred the chicken using two forks and set aside.
5. Make the White Sauce:
   • In a medium saucepan, melt the butter over medium heat. Add the flour and whisk continuously for 2-3 minutes until smooth and bubbly.
   • Gradually whisk in the milk and heavy cream, continuing to whisk until the sauce thickens and is smooth. Add salt, pepper, and nutmeg, stirring to combine.
6. Assemble the Lasagna:
   • Spread a thin layer of white sauce on the bottom of a 9×13 inch baking pan. Place a layer of lasagna noodles over the sauce.
   • Spread a layer of shredded chicken over the noodles, followed by a layer of sautéed mushrooms and spinach, and then a layer of white sauce. Sprinkle with mozzarella and Parmesan cheese.
   • Repeat the layers, ending with a generous amount of cheese on top.
7. Bake the Lasagna:
   • Cover the lasagna with aluminum foil and bake in the preheated oven for 30 minutes. Remove the foil and bake for an additional 15-20 minutes, or until the top is golden and bubbly.
8. Cool and Serve:
   • Allow the lasagna to cool for 10 minutes before slicing and serving.