Preheat oven to 400° Fahrenheit. Lightly spray 9x13 baking dish with neutral-flavored cooking spray, covering bottom and sides of dish completely.
Place 4 large boneless, skinless chicken breasts in baking dish. Note: if chicken breasts are very large or thick, first place chicken breasts on cutting board. Trim chicken breasts, then pound each chicken breast until evenly thin, making sure all chicken breasts are same size and thickness. Alternately, use sharp knife to halve chicken breasts horizontally, creating thin cutlets.
Sprinkle 1 teaspoon garlic powder, 1 teaspoon Italian seasoning, plenty of salt, and plenty of freshly cracked black pepper over chicken breasts in baking dish, covering chicken breasts evenly. If desired, flip chicken breasts over and repeat seasoning on other side. Set baking dish aside.
Add ½ cup heavy whipping cream, ½ cup chicken stock, ½ teaspoon crushed red pepper flakes, and 1 tablespoon all-purpose flour to large mixing bowl. Whisk ingredients together until fully incorporated, with no clumps of flour remaining.
When flour is fully incorporated, add ¼ cup grated fresh parmesan to bowl. Whisk until parmesan is fully incorporated.
Pour cream mixture into baking dish, covering and surrounding chicken breasts.
Spread ¼ cup julienned sun-dried tomatoes evenly over tops of chicken breasts.
Sprinkle ¼ cup grated fresh parmesan evenly over tops of chicken breasts.
Place baking dish in preheated oven. Bake chicken 20 minutes.
After approximately 20 minutes, check internal temperature of chicken breasts with internal meat thermometer. When temperature reaches 160° Fahrenheit in thickest sections of chicken, remove baking dish from oven and set aside.
Let casserole rest 5 minutes. After 5 minutes, transfer chicken breasts to serving plates. Garnish chicken with chiffonaded fresh basil, spoon additional sauce from baking dish over chicken, and serve immediately with mashed potatoes, boiled noodles, or steamed rice.