Preheat oven to 375°F. Spray a 9x13 baking dish with non-stick spray, and set aside.
Use a sharp knife or kitchen shears to (butterfly) cut the chicken breast horizontally almost in half. Set chicken aside.
Mix all of the seasoning ingredients together. Sprinkle the seasoning over both the insides and outsides of the chicken breasts.
In a medium bowl, combine softened cream cheese, mayonnaise, parmesan, mozzarella, garlic, and chopped spinach.
Divide the spinach stuffing into four equal parts and spoon it into the chicken centers. Using toothpicks, secure the stuffing inside.
Place the chicken breasts in a prepared baking dish. Bake, uncovered, for 30-40 minutes, depending on how large your chicken breasts are. Use a meat thermometer to insure chicken is cooked through to 165°.