Preheat the oven to 375°F (190°C). Grease a 9×13-inch baking dish.

Cook lasagna noodles according to package instructions if not using no-boil varieties. Drain and lay noodles flat on a tray.

Heat 1–2 tablespoons olive oil in a large skillet over medium heat. Add chopped onion and cook until softened, 4–5 minutes. Add minced garlic and cook 30–60 seconds until fragrant.

Add shredded cooked chicken to the skillet and stir to combine. If your chicken is cold, warm it through.

Stir in chopped spinach and cook until wilted (about 2–3 minutes). If using frozen spinach, make sure excess moisture is squeezed out before adding. Season with salt, pepper, and a pinch of Italian seasoning.

In a separate bowl, whisk together room-temperature cream cheese, heavy cream, and Italian seasoning until smooth. Warm it slightly if needed so it’s easy to pour.

Spread a thin layer of the cream sauce on the bottom of the baking dish to prevent sticking.

Lay the first layer of noodles, spread one-third of the chicken-spinach mixture, and drizzle/pour one-third of the cream sauce over it. Sprinkle a light layer of mozzarella and a little Parmesan.

Repeat layers (noodles, chicken mixture, cream sauce, cheeses) until ingredients are used, finishing with a generous layer of mozzarella and Parmesan on top.

Cover the baking dish tightly with foil and bake for 25 minutes. Remove the foil and bake for an additional 10–15 minutes until the cheese is bubbly and lightly golden.

Let the lasagna rest for 8–10 minutes before slicing so it sets and slices cleanly.