01 - Preheat the oven to 400°F. Grease a 9x13-inch baking dish with cooking spray or butter.
02 - Season both sides of chicken breasts with salt, pepper, and Italian seasoning. Place them in a single layer in the prepared baking dish.
03 - In a medium bowl, whisk together heavy cream, grated Parmesan, minced garlic, and red pepper flakes until well combined.
04 - Pour the cream mixture evenly over the chicken. Scatter sun-dried tomatoes and spinach around the chicken pieces.
05 - Sprinkle shredded mozzarella cheese evenly over the top of the casserole.
06 - Bake for 25-30 minutes, or until chicken reaches an internal temperature of 165°F and cheese is melted and golden brown.
07 - Let the casserole rest for 5 minutes before serving. Garnish with fresh chopped basil if desired.