01 -
Set your oven to 500°F. Lightly coat a 13x9-inch baking dish with cooking spray and set aside.
02 -
In a medium bowl, mix together the mayonnaise, sour cream, parmesan cheese, black pepper, and garlic salt until smooth and well-combined.
03 -
Layer the fresh spinach in the bottom of the prepared baking dish. Place the uncooked chicken breasts on top of the spinach. Spread the creamy sauce evenly over the chicken breasts.
04 -
Sprinkle the shredded Monterey Jack cheese over the top of the casserole.
05 -
Place the dish on the bottom rack of the preheated oven and bake for 20-25 minutes, or until the chicken is fully cooked and the spinach has wilted.