Preheat your oven to 375°F (190°C). Cook the lasagna noodles according to the package instructions, then drain and set aside.
In a medium saucepan, melt the butter over medium heat. Once melted, whisk in the flour and cook for about 1-2 minutes to form a roux.
Slowly add the milk to the roux, whisking continuously to avoid lumps. Cook until the sauce thickens and coats the back of a spoon, about 5-7 minutes.
Stir in the Parmesan cheese, garlic powder, onion powder, and Italian seasoning. Season with salt and pepper to taste.
In a large bowl, combine the cooked chicken, half of the mozzarella cheese, and the chopped spinach. Mix well.
To assemble the lasagna, spread a thin layer of the white sauce on the bottom of a 9×13-inch baking dish. Place three lasagna noodles on top.
Spread half of the chicken mixture over the noodles, followed by dollops of ricotta cheese. Top with another thin layer of white sauce.
Repeat the noodle layer, chicken mixture, ricotta, and white sauce one more time.
Finish with the final layer of noodles, remaining white sauce, and sprinkle the top with the remaining mozzarella cheese.
Cover the dish with foil and bake in the preheated oven for 25 minutes. Remove the foil and bake for another 10-15 minutes, or until the top is golden and bubbly.
Let the lasagna sit for about 10 minutes before serving to allow it to set.
Variations & Tips
For a lighter version, you can substitute whole milk with skim milk and use low-fat mozzarella and ricotta cheeses. If you’re looking to add more vegetables, consider adding sautéed mushrooms or bell peppers to the chicken mixture. For those who prefer a bit of heat, a pinch of red pepper flakes in the white sauce can add just the right amount of kick. Also, feel free to use leftover turkey instead of chicken for a post-holiday twist.
