Gather all ingredients. Preheat oven to 375 degrees F (180 degrees C). Coat a 2-quart baking dish with nonstick spray.

Combine crushed croutons, Parmesan cheese, and butter; toss to mix. Set aside.

Place chicken breasts between 2 sheets of plastic wrap. Pound to an even thickness with a meat mallet.

Sprinkle with pepper and salt on both sides and place chicken into the prepared baking dish.

Stir together salad dressing, sour cream, and flour in a small bowl.

Spoon salad dressing mixture over chicken and turn to coat.

Top with crouton mixture.

Bake in the preheated oven until topping is browned and chicken is longer pink in the center and the juices run clear, 25 to 30 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C). Garnish with parsley.