Cut a pocket along the length of each chicken breast, for the filling to be placed into.
Rub a little oil over the chicken breasts. on a cutting board and drizzle with olive. Season the breasts with salt and pepper.
Mix the cream cheese, mayonnaise, Parmesan, garlic, parsley, salt and pepper together till combined.
Place approximately 2 tablespoons of cream cheese mixture side each pocket and spread out evenly in the pocket. Divide the spinach leaves amongst the 4 fillets and place on them on top of the cream cheese mixture inside each chicken fillet. Press the top of the fillet down to compress slightly.
Place the chicken fillets into a 9” x 13” baking dish and top with the remaining cream cheese mixture, spreading it out on top of the chicken. Sprinkle the fillets with the grated mozzarella cheese.
Bake uncovered in the oven for 25 to 35 minutes, or until the chicken is cooked through.
Serve with your favorite side of vegetables, such as green beans or broccoli, or with a simple salad.
Sour cream or yogurt can be switched for the mayonnaise.