As chicken bakes it releases natural juices and since this recipe uses a baking dish, those juices have nowhere to go except to pool at the bottom of the dish. You can try these tips to prevent this from happening:  Searing the chicken first will help lock in the juices. While this is not a necessary step for this recipe, if the pan juices bother you, you may want to try it.  Prevent overcrowding your baking dish by spreading the chicken pieces out. This will help create a thinner layer of liquid which will evaporate more quickly while the chicken bakes.  If the Parmesan mayo chicken is still runny after those tips, just simply drain the juices. However for me, the juicier and saucier, the better when it comes to chicken.