1. Make the White Sauce:

• In a medium saucepan, heat 1 tablespoon of olive oil over medium heat.
• Add the chopped onion and sauté for about 3–4 minutes until softened.
• Stir in the flour and cook, whisking constantly, for 1 minute to eliminate the raw flour taste.
• Gradually pour in the milk while whisking to combine smoothly.
• Simmer the mixture, stirring often, until it thickens—about 5–7 minutes.
• Season with salt and pepper. Remove from heat and set aside.

2. Prepare the Spinach Filling:

• In a large bowl, combine the thawed and drained spinach, ricotta cheese, shredded mozzarella, Parmesan, beaten egg, and fresh basil (if using).
• Mix until evenly combined.
• Season with a pinch of salt and pepper. Set aside.

3. Grill the Chicken:

• Preheat a grill pan or outdoor grill over medium-high heat.
• Rub the chicken breasts with olive oil, then season with garlic powder, paprika, salt, and pepper.
• Grill each breast for 6–7 minutes per side, or until the internal temperature reaches 165°F.
• Let the chicken rest for 5 minutes, then slice it thinly or chop into bite-sized pieces.

4. Preheat Oven and Prepare Dish:

• Preheat your oven to 375°F (190°C).
• Lightly grease a 9×13-inch baking dish with oil or nonstick spray.

5. Assemble the Lasagna:

• Spread a thin layer of white sauce on the bottom of the baking dish.
• Layer 3–4 no-boil lasagna noodles over the sauce, slightly overlapping.
• Spoon and spread ½ of the spinach mixture over the noodles.
• Add a layer of half the grilled chicken.
• Drizzle with a bit of white sauce.
• Repeat with another layer of noodles, spinach mixture, remaining chicken, and more white sauce.
• Add a final layer of noodles and cover with the remaining white sauce.
• Sprinkle with 1 cup mozzarella and ½ cup Parmesan cheese.

6. Bake the Lasagna:

• Cover the dish with aluminum foil and bake for 25 minutes.
• Remove foil and bake uncovered for an additional 15–20 minutes, or until the top is golden and bubbly.
• Let cool for 10 minutes before slicing and serving.