In a large bowl, mix the cooked pasta, marinara sauce, spinach, bell pepper, garlic, and Italian seasoning until well combined. Season with salt and pepper to taste.
Spread half of the pasta mixture evenly on the bottom of a greased 9x13 inch baking dish.
Place the chicken breasts on top of the pasta layer and season them with salt and pepper.
Spoon the ricotta cheese evenly over the chicken.
Layer the remaining pasta mixture on top of the ricotta-covered chicken.
Sprinkle the shredded mozzarella and grated Parmesan evenly over the casserole.
Cover the baking dish with aluminum foil and bake for 25 minutes.
Remove the foil and continue to bake for an additional 15 minutes, or until the cheese is bubbling and lightly golden.
Allow the casserole to rest for 5 minutes before serving. Garnish with fresh basil leaves.
Notes
Allow the casserole to rest before serving for better slicing.