1-First, preheat the oven to 500°F and lightly spray a 13 x 9-inch baking dish with cooking spray to keep everything from sticking. This high heat helps the chicken cook quickly while making the cheese bubbly and golden.

2-Next, combine all the creamy sauce ingredients in a bowl, mixing the 1/2 cup mayonnaise, 1/2 cup sour cream, 1/2 cup grated parmesan cheese, 1/2 tsp ground black pepper, and 1 tsp garlic salt until smooth.

3-Then, layer the fresh spinach in the bottom of the baking dish, using the full 8 oz to create a nutritious base. Place the uncooked chicken breasts on top of the spinach, arranging the 1 lb (or 2 chicken breasts cut in half crosswise) evenly. Spread the creamy sauce mixture over the chicken for that rich flavor, and finally, sprinkle the 8 oz shredded Monterey Jack cheese over the top to form a melted, cheesy crust.

4-Bake on the bottom rack for 20-25 minutes, or until the chicken reaches an internal temperature of 165°F and the spinach wilts perfectly. Let it cool for a few minutes before serving to lock in those flavors. This easy creamy spinach chicken casserole recipe adapts well, like using plant-based swaps for dietary needs, making it a go-to for everyone.