Cook the Pasta: In a large pot, bring salted water to a boil and cook the pasta until al dente according to the package instructions. Drain and set aside.

Prepare the Sauce: In a saucepan, melt the butter over medium heat. Add the chopped onion and garlic, sautéing until soft and fragrant (about 2–3 minutes). Stir in the flour and cook for another minute to form a roux. Slowly whisk in the milk and heavy cream, stirring constantly to avoid lumps. Add the Parmesan cheese, thyme, salt, and pepper. Stir until the sauce thickens and the cheese is fully melted. Remove from heat.

Combine the Ingredients: In a large mixing bowl, combine the shredded chicken, spinach, cooked pasta, and the creamy sauce. Mix until everything is evenly coated.

Bake the Dish: Preheat your oven to 190°C (375°F). Grease a baking dish and pour the mixture into it, spreading it out evenly. Sprinkle additional Parmesan cheese on top for a golden crust.

Bake: Place the dish in the oven and bake for 20–25 minutes, or until the top is bubbly and lightly browned.

Serve: Remove from the oven and let it rest for a few minutes before serving. Pair with a crisp green salad or crusty bread for a complete meal.